Well if I can suggest a possibiliy, not just based on SSB Brawl, but also the DBZ Budokai games. I'm close to pulling together an Inuyasha and a Koga cosplay, and I wanted to fuse them together to form Inu-Koga. If I did do Inuyasha for the film, could the fusion be a great final smash effect?
Just thinking about effects for the battle scene to throw out there.