This is my take on what 5th E should be. Feel free to tear it apart.

Classes and Sub-Classes
Each class can be taken as a stand alone class or a more specialized variety can be taken. Some classes are so specialized that they don’t have any sub classes. Any race can be any class.
Melee
Fighter
Slayer
Duelist
Barbarian
Rogue
Thief
Swashbuckler
Spy
Ranger
Scout
Hunter
Warden
Assassin
Ninja
Marksman
Samurai
Kensai
Ronin
Gladiator
Divine
Priest
Templar
Hospitaler
Seer
Paladin
Cavalier
Blackguard
Warlord
Shaman
Witch Doctor
Rune Priest
Warlock
Witch
Binder
Evoker
Druid
Sentinel
Protector
Arcane
Wizard
Invoker
Summoner
Illusionist
Elementalist
Fire Mage
Air Mage
Earth Mage
Earth Mage
Sorcerer
Cosmic
Dragon
Chaos
Artificer
Battlesmith
Tinkerer
War Forge
Bard
Skald
Blade
Troubadour
Necromancer
Surgeon
Psi
Battle Mind
Psi-Blade
Psion
Ardent
Crossover Classes
Swordmage (Melee and Arcane)
Bladesinger
Hexblade
Avenger (Melee and Divine)
Street Avenger
Ghost Walker
Monk (Melee and Psi)
Street Avenger
Pugilist
Races
The races that can be selected should be something more akin to that of 2nd E with rules allowing the conversion of monsters as with permission of the DM. Several of the races allowed in 4th E probably shouldn’t be allowed as playable races. This being said I am not a fan of the human centric perspective of the game. I have always disliked the restrictions that some races received over humans because of the simple argument of “Why would anyone want to play a human if there are no advantages to playing one”. That answer is really quite simple, because of the role playing aspect of playing one. Several books in the fantasy and sci-fi genres can be quoted in having races that are just plain and simply better than humans. These races are still main characters and very interesting to play. This was one aspect that I liked about 3rd and 4th editions.
That being said humans still received several boons that should not be gained. I am not sure how it is assumed that humans will always know more or learn faster than other species but this is just ludicrous. Unless the game is going to reflect it by saying no race is as intelligent as what humans are, then those boons should be removed from the game. The one benefit that humans have is the ability to adapt to nearly any hardship that they encounter and eventually overcome it.
This can be sheer stubbornness on their part, if so why do Dwarves not get the same bonuses as humans. If it is because of their ability to reproduce faster than other races, why don’t Orcs get the same bonuses since they reproduce even faster than Humans? If it is because they are most attuned to magic and that it helps them out is some way. Then why don’t the Elves get the same bonuses since it can be quoted in many sources throughout fantasy literature that Humans learned the art of magic from the Elves who had even more powerful magic than even the Humans. Btw where is all that powerful magic now?
This can go on and on with comparisons to nearly every species out there however the short version is that if a species is better than a human in an area great and if they’re not so good as a human in other areas great. However it must be said that there are just some species out there that are clearly better than humans at every corner and should indeed be represented that way. Others have obvious drawbacks yet those drawbacks don’t seem to have any limitation as to how limiting that they can be in relation to a Human’s greatness. Just be fair to all the non-humans out there.
Feats
Drop the number of feats to 1 per 5 levels and only use them for enhancement of classes or races not to define them completely.
Weapon Proficiencies
Bring them back, maybe something like this.
Melee 1/ 2 lvls start with 3
Divine 1/ 3 lvls start with 2
Arcane 1/ 4 lvls start with 1
Psi 1/ 3 lvls start with 2
Also the idea of weapon groups that has survived in one form or another since 2nd E is a good thing. However I think that you should have to devote proficiencies to it in order to lean them as with 2nd E.
Non Weapon Proficiencies
Bring them back, maybe something like this.
Class + Int modifier is the number of skill points that you have start with. Skills cost more depending on how difficult to learn.
Or alternatively all skills cost 1 and you get to select 1 skill per skill point that you have as follows:
Melee 3+ Int Mod + 1 per 4 lvls
Divine 3+ Int Mod + 1 per 3 lvls
Arcane 5+ Int Mod + 1 per 2 lvls
Psi 4+ Int Mod + 1 per 3 lvls
The skill system should be expanded beyond just a handful of skills. After all it ludicrous to think that just because you have training in one aspect of a skill that you have all aspects of that skill just because you have training in it. That is how the current system is set up. I believe that a “secondary skill” system should also be brought back. Whether this is based on the background options as in 4th E or something more akin to 2nd E that is something that needs to be sorted out. It could be even set up that it is based upon the class and/or race of the character but this has the shortfall that not every character is identical to every other character with that combination.
Another option might be to introduce class skills, racial skills and then other skills. This would allow the players to customize their characters to fit their personal preference on an individual basis. This initially would seem like a good place to start IMHO.
To Hit
Bring back something allows a difference in the ability to hit similar to the THAC0 charts or the To Hit charts in 3rd E. Have it based upon the class similar to that in 3rd E as that seemed to work out fairly well from what I seen. The original system IMHO was the most realistic but when the absolutes on the ACs, Stats and nearly everything else was removed the need for a new system was in order. Once again something needs to be tweaked.
Armor Class and Resistances
This system should be similar to the 3rd and 4th E but with a much more subdued outlook. Something similar to the various ACs that is present in the 1st and 2nd E versions. If you truly look at both systems they look different only because they are presented differently. They are actually very similar overall but with some clarity thrown in to make it easier for newer players.
They whole thing about gaining AC when you level up however I do not like in the least. I understand it from one aspect but I don’t feel that every class melee and non melee alike should go up at the same rate. It’s ludicrous to believe that someone who spends all their time in a library and has never seen an actual fight much less been in one, can dodge just as effectively as someone who has been training their whole life in the combat arena.
The one thing that I loved about 3rd E and I thought it should have been there all along are the rules concerning resistances. The way it used to be handled in 1st and 2nd E was ok but it really didn’t feel right. I do believe that the Magic Resistance should be brought back from the 1st and 2nd E however. This might make the system a little bulkier but it does add a little more to the game that I like. However it should be something rare that the players come across. The same applies to creatures. If you give something to everyone it is meaningless.
Increased Damage and Hit Points
Other than spells doing more damage and back stabs doing more damage with levels increases all damage will be the same at 1st lvl as it will be at 5000th lvl. All weapon damages will always be the same.
The only reason a character needs to have insanely more hp than as with previous editions is because the damage potential is out of control. Once you get that under control you can lower the amount of hit points that a character has and still allow them a reasonable chance at living. Just out of curiosity what was wrong with actually rolling for initial hp and new hps when you level? It allowed some randomness to the characters rather than if you have the same cons you know exactly how much hp you will have throughout your career or to the max level allowed.
Specializations
Bring them back.
Do not restrict it to just “single class fighters” rather set it up as a feat that gives all the bonuses as it did in 1st E and 2nd E. Allow for the enhanced specializations at higher lvls as with the combat and tactics type. This allows the basic melee types to really shine rather than being “just a fighter”
Spells, Powers and Abilities
This was, IMHO, the short fall with 4E. The only characters that should have this stuff are spell casters, Arcane or Divine, or Psi types. The ability to have this advantage as a race should be on the weak side and not over powering. This is not MtG where every edition HAS TO BE more powerful than everything before it. If it’s not broke, don’t fix it. As I am not overly familiar with 3E and I am going to have to put this into 2E terms. Other than maybe the Drow there wasn’t a race out there (off the top of my head) that was an optional playable character, which was too overpowered.
This being said I do believe that if a species is a naturally occurring psionic race I do not believe that they should be required to take the psionic classes in order to be a playable race. This decision as to allow the race should fall directly in the hands of the DM. Will this make said races powerful in relation to the rest of the players, of course, but that is where a DM has to run a tight ship sort to speak. The exception I can think of is the Dark Sun setting. That exception, I think that all of the characters should have the option to have at least minor psionic powers regardless of species. This is solely based upon the fact that Dark Sun has always been more psionically attuned that any other setting. The next possibility might be the Spelljammer setting if that is ever re-released.
Other than these few exceptions characters will use weapons and thus be limited to a low base damage. This should be offset with the ability to have multiple attacks. Whether this is coming from higher levels or specialization that is yet to be determined. I would recommend something based on the 2nd E set-up in this case since that edition had the best specialization rules, IMHO. I consider the Player’s Option series to be part of 2nd E.
As far as the various effects and damage types, the whole thing should be downplayed since that really shouldn’t come into play that often. It’s damage and damage is damage. Does it really matter if you were killed by the cold, fire, lightning, acid, poison or a million other damage types? Very little actually. The only time that it should really come into play is how easy it is to bring you back from the dead and if any other spells need to be can to repair damage or neutralize a poison or acid.
Get rid of the whole card portion of the game, UNLESS, you want to put out a setting the is indeed a MtG based setting. This however should be avoided only because it has been my experience that converting any non-role playing game into a role playing game seems to have many failures. That being said those failures can indeed be fixed with lots of work from the players and the DMs in order to produce a workable version. However it will never be the same because is what should be converted is the idea or concept of the base game/ movie/ book. If that can be stressed and not a “direct conversion” things will have a much easier transition.
Multiclassing
This should very well be allowed and in the same manner as 1st and 2nd editions. The player should be allowed to have a full multiclass at first level. Every race should be allowed to multiclass into any class combination. Although I see the benefits to being able to add a class later on I am not sure how this should be approached. I liked certain aspects of the 3rd E method of dealing with this however I disliked the multiclassing method as a whole. Converting characters from 2nd E that were high level were severally depowered even after they had the experience restrictions of the 2nd E which were IMHO fair if you choose to multiclass.
If some hybrid of the 2nd and 3rd E duel classing could be settled upon that would be best as I feel those were the two best systems that have been used. 4th well, let’s just say I am not a fan of in any manner and the hybrid system while interesting, should be it’s own separate thing and not the short and weak version of multiclassing. Some more akin to the Swordmage or the Avenger in their respective roles however this would require the DMG to have rules on creating new classes as with 2nd E.
New Classes
I loved that in 2nd E that the DMG had rules for creating new classes. Although they required a ton more experience to be on par with the original classes it was still and very cool option that was allowed to DMs and players. I strongly feel that this should indeed be brought back to the game especially since new classes and races are being added with every box set.
Magic and Mundane Items
The group that I play with is disturbed over the lack of a magic item creation system. The magic items that do indeed exist do not seem to have any rhyme or reason behind what level that they are required to have. Some seem really powerful and are low level and others are seemingly not overly powerful and are high level. Please fix this with a standardized method of creating magic items similar to either 2nd or 3rd E versions.
As far as seemingly mundane items, there is some difficulty in determining what is actually a mundane item and a magic item since neither seems to have any rhyme or reason at to how that they’re made.
I suggest as simple fix, get rid of the whole level requirements that are on most items. This is simply a need for additional creativity on the part of the players and DMs vs. an attempt to keep everyone from getting anything that might be too powerful too early. This can be fixed by creating charts similar to previous editions in which to roll on in order to reward a group of players. This too was an imperfect system however; at least, it was fair due to random items being generated.
If the class powers are no longer the main aspect of the characters or the game then the game can start to focus on character development and not powers development. The point here is that even though the character should eventually get magic items that they should never be able to go to next door to the pawn shop and buy any magic item that they have the money for that their level allows them to have. Magic items should be rarer than they are rather than having a MtG listing on how much that they are gonna be worth during trades. All magic items should be rare or unique depending on what it is. It should never be a bazaar of the latest and greatest… and all your previous stuff is now obsolete because we want you to buy a new supplement. I am strongly against the raping that takes place when you sell or break you items down into their base components. This is a radically unfair to the characters who spend their lives adventuring and trying to upgrade all their stuff to try and keep themselves and the party alive. I am not trying to say that it should be a 1 to 1 conversion but something a lot more fair than the current system needs to be in place.
Masterwork items really to go back to the 2nd editions rules concerning them. I am not sure how they worked out in the 3rd E so I cannot speculate on that edition. Either way as they currently stand they are confusing and I have been playing this game for over twenty years now and so has my DM and neither of us can seem to fully figure it out. It might be that it’s too simple and that we are reading more into it than we need to but hey being human we are indeed fallible.
Saving Throws
Although I personally didn’t have a problem following the charts in 1st and 2nd E books the newer system for saves does make it easier for new players to learn how to make saves. However it shouldn’t be a 50/50 chance of making the save. Granted it has always been either you do or don’t but it used to be once you were higher level it was much more difficult to miss your save than at first level. Granted you wanted to make your save because if you didn’t you were probably dead.
I suggest a system similar to what I suggested for the To Hit system earlier. The character gets a +1 to make their saves per level. Their overall number that they have to beat is 20. In effect the target number does get lower as you advance in level however you are still trying to beat the goal of a 20 with your bonuses.
Death saves, really???? I am not a fan of them. Let’s face it unless you roll absolutely horrible multiple times in a row, I have seen it and done it, you character will never die, ever. You used to get one maybe two saves vs. something that was devastating that you actually died from. However you never got one to stop dying after you already were and you don’t get one in the real world either unless someone is helping you.
If you’re unconscious and dying the odds of surviving are fairly slim. That is unless someone else saves you with medical treatment. This is how it should be. After all what is the danger of doing all of these perilous activities if there really isn’t a chance of dying. It has become low risk high pay off.
It used to be high risk and maybe you might not die and make a few bucks in the process, if you lived by your wits and didn’t do anything stupid. Sadly the characters have pretty much no reason to not become ruthless killers and thieves and do whatever the hell they want. As it sits we have been killing other sentient creatures for years and enjoying it.
The saving throws should be based upon your level and have something other than a 50/50 chance of making it. I am ok with only having one saving throw for all saves with bonuses based on the type of save that you’re making. However making it more difficult to make saves at lower level and easier at higher levels. That being said you shouldn’t making saves too often at lower levels because the attacks shouldn’t be that devastating.
Healing Surges and Surge Value
At first this was an interesting concept however as time went on the idea became more and more… well less attractive. I don’t understand the line of thinking that a person can only be healed X number of times a day before no amount of healing can help them. I am pretty sure if the Gods so choose to, they could heal anyone/thing as much as they cared to. I also don’t agree with all healings giving back the same number of hit points every time that they are used no matter what outside forces might be trying to interfere with that healing.
Ongoing Damage and Spell Effects
Ongoing damage should be based upon your level and not how well a save throw system works. I won’t beat that bush any more than I have already. The basis of ongoing damage should be fairly straight forward and more predictable. By basing it on your level it has several benefits. First, it allows you to know exactly how long your spell affects are going to last, rather than having a chaos factor with every spell. Second it allows easier tracking capabilities for players and DMs alike. Third it gets rid of having to sustain the power and allows a “fire and forget” type of mentality with most spells.
On the down side it does require a little more up front calculations to make. This is usually fairly simple and can be prepared ahead of time. When you level up for instance or gain a boon from an environmental effect or from another player’s abilities. All of these things can be, for the most part preset or figured in advance as long as communication is present in the group.
Now that all that has been said. I am aware that some of these things are unpopular with the masses but for those who are not willing to take the time to offer up some alternative or even a starting place I am not overly concerned with your thoughts. I am willing to discuss things with people who are willing to do the work on an attempt to make a better proposal.