I think that if we've got 12 or 13 players on then really we need 6 in one room and 6 or 7 in the other. That way everybody gets to be a striker or midfielder and they can have a heck of a lot more fun. Also, it stops everyone from just pressing down on the d-pad and robbing all the good positions. I'm set as a midfielder, and I'm usually playing on the wings in my games, but in all fairness yesterday I did play 3 or 4 games in the different rooms as an LB.
Just to re-iterate my point though. If we've got a game room with a full 10 players in, but then the dressing room only has say 2 players in, we need to be sending some of the game room players into the dressing room so that those guys can join up and play in game room 2. That way everyone gets way more chances to play in their favourite positions. When there's 10 of us all talking at the same time saying they will take up 'X' position then it's very easy for one or two to take others positions without realising.