OMG I LOVE IT <3 RITO PLZ
This would force players to really think about how to make a team work even when it's not that great. Also it would give people an opportunity to try playing champs that aren't op which is sadly what happens in pretty much every game mode.
I can only see one drawback to this, would you be able to pick from all the champs in the game? or only the ones that the other person has? maybe a pool of all the team's champs? If you think about it though that does one of two things. Either it means that if you only have champs you like to play then there's no way to make it hard on you...or you could end up playing a champ you've never touched before and have to madly look up what that champ's skills do. Some thought would have to be given to that, but good idea overall, logged in just for this