User @Remy94 (and maybe others before him) suggested a 2 vs 2 duo battle option. I actually have something similar somewhere on my to-do list; 'team-battle'. The idea is that you can choose up to 6 (Or any other number) characters to battle any other team of characters.
The downside of a team battle is that I can't show stats for any team larger than two characters. It would take up too much space.
Should a team get a calculated 'class' based on its members' stats?
If you have any suggestion or ideas, let me know.