Wouldn't it be cool if CoD was made into an FPS RPG.
I'm thinking a FPS sandbox game like DAYZ except there's no zombies, just war themed gameplay... You join a clan that you always stick with and randomly run into other clans, kill them to gain XP, weapons, gear... Or you can team up with them. Join the game by yourself and find another loner, then you can decide to join or kill each other.
Gain XP to build a base with headquarters, get vehicles and gear.
Let me know if this has already been done in another game, I have no idea since I don't play a lot of games.