Something has just occurred to me. The longer a game goes on/how difficult the objective is, the more teamwork there is. Think about it. Say one team has an absolutely amazing defense going on. The attacking team is then forced to work together and plan an attack.
A perfect example is Goon Haven. The intel is god damn impossible to get by yourself, so that server has almost always the most teamwork.
Now how exactly to do this is the question. Possibly some sort of never-ending kind of match where the goal is almost impossible to obtain, maybe like upping the TC cap to 3-4 people minimum.