If for example I tried to add this rule to 4th edition now, it would need to somehow address all of the powers that grant shifts, the fighter's and any other bonuses on OAs.
"When you are moving out of a threatened square, you may spend an additional square of movement for each enemy that threatens you to move defensively. If you do, you do not provoke any opportunity attacks for that square of movement, but your enemies may use triggered powers as if you shifted. (You and your allies may not use any triggered powers or other benefits that require you to have shifted.) You cannot use this option if an effect prevents you from shifting."
Tada. Shifting still works, though powers that let you shift may be someone lower in relative value now. (Walking and paying the extra squares will almost always beat out the standard "shift" action, for example.) The triggered power clause keeps it from being a cheap way to disable the fighter's CC/CS combo (they at least get to hit with CC), or equivalent enemy powers. And OA bonuses are basically devalued to irrelevance. But overall the game should still work fine. (Aside from the obvious overabundance of mobility on all sides.)
Anyways, the big problem IMO is that this really doesn't stop anyone from doing the spring attack thing, it just slightly increases the amount of movement speed required for the manuever. It's going to be pretty negligible in its effects except that everyone will be noticing how much time they are spending counting out how far they can move when factoring in the extra cost of moving in/out of threatened areas. Especially because of the stacking where it makes exact positioning -even more important- than in the standard OA model, as it will end up determing where you can end up moving to.
I think it'd be much simpler and more effective to have a simple auto-hit rule for OAs. Basically have OAs (4e style preferrable: simple, with few triggers) that automatically hit and do minimum basic attack damage. No dice rolls, quite predictable, strong enough to matter but weak enough to not be overwhelmingly stupid good, and makes a fighter's OA more fearsome than a wizard's.
What I meant was "If for example I tried to add this rule to 4th edition now without completely changing the game's balance, it would need to somehow address all of the powers that grant shifts, the fighter's and any other bonuses on OAs." A great deal of 4th edition was balanced around the ideas of using powers to shift or otherwise move to where you need to be and also applying forced movement to get enemies where you want them. If they had different shifting rules from the start, they would have balanced these powers completely differently.
Aside from the fact that I'm not convinced that giving everyone free spring attack is a good idea, that same problem would still be evident in all manoeuvring. As I said in an earlier post, this movement penalty thing is the exact same OA system as 4th edition, except that shifting is more complicated.
I would feel the same way about auto hit OAs as I do about the Slayer's auto damage ability. They work yes, but I don't think they're very interesting. Most things in D&D are about trying to do something and then rolling some dice to see if you succeed. With standard OAs if you're on 1 HP, you have all of your normal options available (attack, total defence, shift etc.) or you could attempt to move to get further away or use a potion, both of which would provoke an opportunity attack that may drop you. If the OAs are auto hit, you simply lose those last two options.
Honestly, after thinking about it for a while, I don't think we'd gain aything from a movement penalty system other than a "more realistic" way of simulating combat at the cost of making the simulation more complicated and probably significantly harder for new players to understand. It is probably not worth that cost.
As I see it, AoO is used to block "magekillers", correct?
Basically in my opinion, rules should represent some mechanics that seem to work in the real world or in movies. In this case I envision guards protecting someone - attackers provoke which demotivates from attacking someone.
But now, think about it. Let's say we have some royal guards that form a circle around a king: "Protect the king!" (a fighter and a cleric protecting the wizard is a smaller version) Now, apply an AoO system. A fanatical assassin who doesn't care for his own life wants to kill the king. He dashes through the royal guards, takes one or two hits which are not enough to kill him, then he kills the king (I assume that for reasons of dramatic theatre he can do so with one hit, maybe with a poisoned dagger) Is that what we want? If I'd be a movie director, I'd say it might happen and it might not. Applying the current systems, the assassin either can (takes damage but oh well) or can not (not enough movement), or he might try to tumble, which is also about damage. What I would like to see is some kind of guarding mechanism - the guards try to block the assassin with the shafts of their halberds, not priorizing on hurting him but on blocking him while the assassin tries to get through. Basic idea would be that the assassin rolls an attack against every blocking guard, modified by circumstances (+ the weapons are good for such actions since they are long and have hooks, - there's some space between the guards and they need to use the reach of their weapons to cover it, + the guards encircle a small hill that the assassin needs to ascend...) and if it works, he gets through. Or if you find that to be too difficult, let him roll one time and he needs to overcome the highest defense (which is probably not AC but the guards attack modifier) (the "overcome highest" rule is a good one for several other checks btw, just think of stealth vs perception, you have no chance to succeed stealth checks vs 20 different people, even if they all have a very low perception but you can easily overcome the highest in a single check)
As for provoking by casting or using a bow, introduce active defense. You cannot defend very well without a weapon which renders the most dextrous wizard quite weak against attackers. Disturbing a spell becomes an intermediate interrupt that does no damage.
As I see it, AoO is used to block "magekillers", correct?
Not only. It's also a way to make choke-points reasonable. You fight in a choke point (say a door) because it limits the number of enemies that can attack you, but if they can dance in and out then even choke points make no sense.
To those advocating some sort of "social contract": why can't we have good rules too? Starting from your point of view we then don't need rules at all. Saying that "it makes sense in reality" doesn't mean anything, because everybody will have a different opinion about what "makes sense". And by the way, reality doesn't "make sense" quite often.
There's also organized play like RPGA or Encounters where you need to keep a common line among tables.
Moreover the D&D combat engine never made sense at all. The simple fact that you have turns within a round brings combat to an high level of abstraction. Everybody should be moving and attacking at the same time, so the orc you hit here and pushed over the ledge was actually on its way to there and considering your speeds you probably should hit him 10 feet away from here, but then you shouldn't have been able to push him over the ledge and.....I think you can see where we go here.
What we need is a combat system that is fun, reasonably quick and deep (meaning offering interesting tactical and strategic options), and at the end gives a result that more or less looks like a "real" combat. On our way to this goal we may have to sacrifice some aspect in favour of some other but that's life.
Ksorkrax - One way I can think of to implement your idea would be to have stances. Basically you choose which stance you are in at the start of each turn and you gain its benefits until next turn. The basic stances that everyone has access to could be:
Aggressive Stance: increase your weapon damage by one dice category.
Opportunistic Stance: you can make OAs using the 4th edition rules.
Defensive Stance: you gain a +1 Bonus to AC against one enemy you specify when you activate the stance, your speed is reduced to 1 (unless it was already 0) and your movement doesn't provoke OAs.
Classes could learn new stances of their own at different levels:
[Fighter] Improved Defensive Stance: as defensive stance and you stop the enemy's movement whenever you hit with an OA.
[Rogue] Scouting Stance: you gain a +2 Bonus to speed and if you move more than 20ft in a single action, you gain advantage against the next melee or ranged attack that targets you before next turn.
[Barbarian] Vengeful Stance: you gain advantage for any attack against an enemy that has damaged you since your last turn.
[Wizard] Focussed Stance: insert the 3.5 defensive casting rules here.
I am in favor of anything that doesn't include "attack." Out-of-sequence combat actions are a huge drain on combat time; one of the best parts of 5.0 so far is the lack of them. I like the simplicity of making it extra movement, and you need an option for when people don't want to pay the movement cost. However, you quickly risk too much complexity.
Moving out of a threatened square costs one extra movement. You can avoid this movement penalty but you take disadvantage on any action you make this turn.
Done. Makes withdrawing possible without extra rules and still penalizes movement through melee. Anything more complex is starting to get too much to remember. Allowing the threatener advantage is more to keep up with than allowing the mover disadvantage: plus the entire range of consequence is handled on the same turn as the invoking incident.
I may just houserule that on our next play session and see how it runs.
I really like the above option. Quick, simple, and easy. For those who want to get back to a more tactially challenging and/or risky kind of fight, I have tried out the option below in some quick test combats and it's worked nicely, but without bogging down the game in tons of extra actions like OA's and AoO's sometimes did:
If you really liked OA's or AoO's and want to keep that concept, I'd consider this: If somebody does something that would reasonably provoke an OA from a given individual, it instead affords them the option to move UP in the initiative order for that round ONLY, as if they had been higher up and had readied an action to attack or intercept the target if it took whatever action provoked the reaction. Note that this is not an extra attack or action, it only allows you to move up the initiative order to take your action sooner, due to the target's sudden vulnerability. I would also apply Disadvantage to any attack made, due to its hurried nature.
This way, you don't have any more actions going off per turn than you already had, but it fills the same sort of role the OA did, without bogging down the game with EXTRA attacks. It would only add a few moments to a given turn by way of interrupting the intent of the provoking character.
I might also consider limiting how much further a character can move up in initiative, to represent that an extremely spry individual who has rolled an initiative of say 18 for the encounter, would be able to slip past or away from a slowpoke who rolled only a 5 or 6. Maybe cap it based on your Dex score (actual Dex, not just Bonus), so somebody with fast reflexes is BETTER at rushing to intervene or strike at a moments notice than somebody with slower reaction time.
The last bit would add a level of calculation in that would somewhat slow the game, but you'd only have to figure it once per encounter. Roll initiative and keep track of that ofcourse, then add your dex and keep track of THAT as your (just for instance) Reaction Score for the encounter, which would then just be compared to the initiative that any provoking character is acting on to determine if you can interrupt.
I quite like Gurka's suggestion. But I think it has a couple of problems.
I wouldn't describe it as moving their Turn up in the initiative order for two reasons; the first being that if you roll highest initiative, you can't move up and the second being that there's no reason to describe it as a change in initiative order if it is only for a single action, 4th edition for example allowed reactions and interrupts to be used when it wasn't your turn.
Instead, I would write it as something along the lines of: if a creature provokes an OA from you, you can interrupt their turn and make a single melee attack against them as if you had readied an action to do so. If you do so, you gain advantage for the attack and your position in the initiative order is moved to be immediately before that creature.
The reason I changed disadvantage to advantage is pretty straightforward. If someone doesn't see it as absolutely necessary to kill you right now, it's much better for them to not OA you and make an attack without disadvantage against whoever they were fighting (or even against you if they were free to move after you) because the OA would use up that same action for the same attack except that they'd have disadvantage, which is also why I gave them advantage instead of just a normal unmodified attack.
Now that they have the ability to make an attack with advantage, they have to do so at the cost of their movement for that turn (because their turn would have had to take place before the provoking creature's this round just like triggering a readied action).
I would definitely avoid limiting the people you can OA by your initiative score, firstly because it imposes an arbitrary restriction on who can and can't OA you, yes initiative is based on speed but it doesn't mean much after the first round because after that everyone is just taking turns at the same speed.
Another reason is that it would add an odd sort of metagaming to the tactical movement rules; before you move you determine who can OA you by doing some wierd math based on Initiative scores. Yes, when I say wierd math I mean wierd math. If I roll 25 initiative and my two enemies roll 1 and 10, who can I OA with my +5 Dex modifier? My initiative certainly isn't within 5 of either of them, do I wrap around to 0 so I can only OA one of them? If that's the case, then I can basically only ever OA people who roll 5 or below. If you instead wrap it around to the lowest initiative, then the guy with 1 initiative is actually protecting mr 10 from me by being so slow. If mr 1 dies, then do I suddenly gain the ability to OA mr 10?
The first contention doesn't really apply since, if you rolled highest on initiative, you would have had to hold your action anyway for it to still be available to interrupt on somebody else's action later. If you act normally at your initiative, then you're spent for that turn. Your comment did, however, make me realize that if you're already holding your action contingent on something, you shouldn't suffer the Disadvantage penalty for exploiting somebody else's sudden vulnerability, since you're not really unprepared. It might not be the specific action you were ready for, but you were ready for something, as opposed to moving up from a lower value. In that case you're not ready for it at all, hence the penalty.
Second, I wouldn't want it to be strictly limited to an attack. If somebody wants to try and move past you to a more vulnerable target, intervening to simply block them should be a valid option, I think, as well as certain other things that aren't likely to come to mind until you're in that particular scenario.
I also don't like giving the interrupter any kind of advantage for it, since acting before their initiative would normally allow them to is already a bonus, earned by intelligent tactical positioning. I still like throwing the disadvantage on any action taken for that reason. I want it to be a decision on whether or not to use the opportunity presented, not a no-brainer. You have an initiative score that you rolled for a reason, so even if somebody opens themselves up to an attack or intervention, the "advantage" therein is by allowing you to act sooner than you would otherwise be able to. I think it should still be numerically advantageous for a character to act when they are ready based on the initiative they rolled, but it might be situationally advantageous for them to act sooner if the opportunity presents itself.
Giving up your move if you interrupt isn't a bad idea. I might be a viable replacement for the Disadvantage, or perhaps you're offered a choice: if your interrupt is something that Disadvantage can affect, then you can chose to take the disad or give up your move, and if it's something that doesn't require a roll, then you default to losing your move.
I do agree with your point about restricting who can interrupt who, particularly on the point of metagaming. While I don't view it as an arbitrary or illogical restriction (think about football; even when they're ready for it and within arms reach, defensive players often can't shift their momentum or predict a skilled runningback's moves well enough to catch them), a static value definitely isn't the way to go, and there probably isn't a reason to include that kind of general mechanic at all. It might be better handled by offering a feat to some or other background that makes it more difficult or impossible for enemies to interrupt the character, by virtue of them being exceptionally quick or agile.
As for the bit about Weird math, I think you kindof misunderstood where I was going with the restriction in terms of numbers, but you definitely brought up a good point none the less.
However you want to interpret the rules for the purpose of narrative, my first contention is perfectly valid from the perspective of mechanics. By your logic, rolling highest on initiative offers a disadvantage by preventing you from ever making OAs unless you delay. People who reacted slower to the fight get the ability to OA and people who reacted quickly either can't OA or need to give up the advantage they gained by reacting quickly so that they can OA.
With regard to the free advantage/disadvantage on OAs, imagine the following situations:
If OAs give disadvantage:
You provoke an OA from me. Even if I know I could kill you with a single hit, chances are I won't take it because disadvantage makes it less likely that I'll hit. If I don't know I could kill you with a single hit, I'm even less likely to take it because waiting and attacking normally would be better.
A wizard is surrounded by 8 enemies. He can either Dodge (+4 AC, uses his action) or he can cast a spell. Guess what happens when he casts the spell? If the enemies take their OAs, they've now wasted their turns for an attack they could have made anyway except that they made them with disadvantage. If they don't take their OAs then the OA mechanic becomes fairly pointless.
A fighter is trying to tank a group of enemies. What's his best option for doing so? With the disadvantage on OAs, he can sprint around the room provoking OAs from everyone. No one has any incentive to waste their action for a worse attack, especially on the PCs tanking character so none of them take their OAs. Great, now the fighter has just cartwheeled around the battlefield and no-one cares. In many situations it would become more effective for the fighter to waste his turn trying to provoke as many OAs as possible so that the enemies can't attack his allies.
If OAs have neither:
a) Still a similar problem to above, if I'm not attacking you in the first place and you try to run past me with more than a few HP, there's very little incentive for me to actually use my action to attack you instead of the enemy that I actually wanted to fight. b) If I was already fighting you, your movement lets me make an attack first in the same way that high initiative lets me make an attack first. If you keep retreating at the same speed I follow, we still make one attack against each other per round. If you then stop retreating, the point in time when I can make my attack returns to where it was by default in the initiative order. If it's a 1v1 fight, all you have to do is stop provoking OAs when you're 1 hit from death and any advantage I may have gained by acting quickly in previous rounds is lost because I now have to return to my normal turn and you aren't dead anyway.
Ok, now there's no reason for the enemies not to take their OAs. But what about the wizard? He can do something that doesn't provoke OAs and have the enemies attack him during their turn anyway or he can cast a spell (which is probably far better than the other option anyway) and take the exact same damage he would have taken in their turn anyway.
Doesn't fix this problem either. The fighter can still use cartwheeling as his most effective way to stop enemies from attacking his team and the enemies still have no incentive to actually take their OAs against the tank because they want to attack his team first.
If OAs have advantage:
Fixed, there's now a good reason for me to attack someone who provokes an OA by leaving themself open, even if they weren't the creature that I was previously trying to kill.
Fixed again, the wizard is now choosing between casting a spell and taking attacks with advantage or doing something that doesn't provoke OAs and taking their normal attacks without advantage.
Guess what mr cartwheels, if you do that you're actually pretty easy to hit. Now the enemies have a better chance of actually hitting the fighter so taking the OAs that he provokes has become an attractive option. The fighter can still go around soaking up as many of the enemy actions as possible, but it hurts him more than it would if he wasn't unning around like a headless chicken.
In previous editions, whether or not you took the opportunity to hit someone who let their guard down was a no brainer. With this rule giving you advantage but costing you your entire turn, it becomes a choice. Where previously, provoking an OA would often mean the enemy attacks you twice that round and you attack them once, now you attack each other once but he has advantage.
The main reason for losing your movement when you OA is because of the initiative change. Changing initiative is the simplest way of taking away your normal action for that round and it is perfectly consistent with the rules for readying an action.
On your point about stopping movement, the current rules would seem to put that under the category of improvisation. Tell your DM you want to stop him from getting past instead of hurting him, make an opposed strength check against them with advantage (or without, unfortunately depending on your DM by the very nature of the improvisation "rules"), if you win you can stop them from moving.
I can't think of any possible situation where you would be interrupting someone by doing something that doesn't require a roll (an attack, stopping them from moving, whatever). So whether making an OA grants you advantage or disadvantage, it can always be applied.
Thinking about football isn't a particularly advisable idea in my opinion. Firstly because I don't like it, play it, watch it played or even know most of the rules on how to play it and secondly because as far as I know, football isn't turn based so it's interpretation would need to change completely for it to work on a turn based game.
I don't agree with the way you are thinking about Initiative. You are treating it as if it reflected how fast you are, when it doesn't really. It reflects how fast you were to react at the start of the fight, but it doesn't really indicate any sort of speed after that. Dexterity on the other hand is supposed to determine how fast and agile you are, it gives you AC that already makes it harder for OAs to hit you without needing another mechanic to determine if an OA can hit you on top of that, especially when that other mechanic is based off a value mostly determined by a single d20 roll at the start of the encounter rather than your actual stats.
That wierd math was the only way I could think of to interpret what you explained. Maybe you meant that the guy with initiative 8 and +3 Dex could OA anyone with 11 or less initiative? If not, would you care to explain?