Not sure if anybody else yet has brought this up, but what if there were some sort of option in versus for both players to choose either tag or solo fight for their selection? Balancing could be handled as giving the solo character a buff (definitely more health lol) or a separate mechanic, and vice versa. I think it could be fun and interesting... Story mode could have your characters paired together in tag battles. Think Kenshi with Takeda, or Johnny with Cassie vs. a buffed Kotal lol.