Suicide Squad has a cast so large it opens up numerous duo dynamics. An original and changing co-op mode encourages a multiplayer system in a world where gamers will settle for nothing less.
In a good BioWare game, your party members talk to one another, and the conversations change depending on who you have with you. Over time, the dialogue progresses based on previous interactions. Why not have the same story shifts based on your main character selections in Suicide Squad?
And it may be asking too much, but it'd be nice to see the actual missions adapt to the number of players, or to have two-player attack combos open up.