Quote from twizHowever to do this we'd have to have someone do some coding, we'd need the rebels to act like enemies and the combine guys to act as teammates.. I don't know how hard that'd be to switch them around.. maybe as simple as re-naming the models so they get switched in-game?
That's not necessary, just use an ai_relationship entity in Hammer and set the rebels to hate the player and the combine to adore him.