It wouldn't be too hard. You'd just do some clientside texturing. Hell you could make the fuckin things show through walls if you wanted.
Texturing it is the easy part, I'm talking about the different classes seeing the same model but with a different material on it. The same players in the game. One day, I will ween myself off mousewheel weapon switching. I use numbers in every game now, except Empires, where I'm just too used to using my mousewheel.