Just an idea about having same players being able to go on the same team to allow say one player to de economy while another player controls the army side of things. They did this in starcraft 1 and I havent seen it since. It looks like they are doing it in stronghold crusaders 2 I read. Would be a cool option I think. Not sure if each player would have a commander or what, but something to think about.
Already implemented, try the team game mode. In it players will be controlling the same army and the other can do the economy while the other handles army (if they want to).
