If they sign up then surely they at least do a battle to get the loss rewards? You get the dailies without even signing up, so why bother signing up if you're not going to get the loss crystals and 8th place at least?
I don't see how op can get more than 10 banners, then if the other guy even starts and forfeits he'll win on gp tie breaker.
Most of the mm complaint threads the person who made the thread will win if they can kill a character. This one can't kill a character, unless the opponent has made the effort to set only a partial defence, or a very very very low team on purpose. I guess they might have a completely empty defence.
Actually, on reflection, it seems like a completely empty defence is the only way that roster could be in carb4, if the owner has any interest in collecting crystals at all.