c) Pick The Winners (game-modes)
- Sure, you can have all kinds of game-modes, but only a few are competitive and supported as such. In team games, each side must play the same faction if in competitive mode. Yes, it is not as flashy, but it drastically cuts down on balance pitfalls.
I don't know any game that would force whole team to play same faction/class/character/whatever. But they will most probably again release a game with only 2 factions at the begining so you have it covered at the release.