If you must tie something like alignment to mechanics use other terms like holy, unholy, extraplaner, primordial, ect....
So the Paladin gets a 'holy aura' if he worships a good god wich means the game mechanics that effect 'holy' work on him, but not his lawful good ranger friend.
The demon prince has an 'unholy aura' and can be smited by the good paladin and prevented from entering the warded temple. But the chaotic evil assassin sneaks though the wards like they are not there and paladin can't pin point him in the gathered crowd with his detection powers.
Also no penalties for switching alignment, just let players play them like they want to. Now if you have one of these 'holy auras' then yes you can violate a code of ethos and beforced to take on another aura or change something up.
In 3.5 and Pathfinder most power gamers just picked to be true neutral so they were not effected by spells like unholly word, or certian weapon enchantments.
Remember this is a public forum where people express their opinions assume there is a “In my humble opinion” in front of every post especially mine.
Things you should check out because they are cool, like bow-ties and fezzes.
https://app.roll20.net/home Roll20 great free virtual table top so you can play with old friends who are far away.
http://donjon.bin.sh/ Donjon has random treasure, maps, pick pocket results, etc.. for every edition of D&D.