Shuffle Queues!
Ever play with your friends and wonder what it would be like to play against them in a normal queue setting? That way you can really see where their strong points are and compare your skills. Introducing shuffle queues where teams get together but once matchup begins the teams are automatically shuffled; that way you can play against some of your friends in a real game setting without having to come up with 10 people for a custom game. (as i was writing this i now think it would be easily implemented as an option in teambuilder)