I'm curious what you're planning on doing for this, since it sounds like it's going to be pretty clumsy to set up teams for each battle. My idea: finally implement the Friends lists. And every mutual friend of mine (has to go both ways) is added to my permanent co-op pool. Then, when I start or join a co-op battle, the server checks if anyone in my pool is available (online and not in battle) and automatically invites them to the battle. It could even display the number of available partners at the top of the screen so I can tell at a glance if I've got enough friends online for a 5 vs 5 battle. This would also serve as an in-game guild system.
There should be a real guild system implemented, usualy it's one of the priorities of any mmorpg. You come to test the game, you finish the campaign caus the game is good and you stay forever caus the community is wonderful.
We're definitely keen to hear more thoughts about this area. I believe our current plan has just one step, being: Plan this
