One thing i would like to see is a Tournament Mode for Online, and mabey have the characters ultimate attacks similar to Budokai 3. they were always fun to watch during a battle. each was different but with the same planet destroying explosion. i would spend hours playing with it to see the different outcomes of the tecnique. to ether get a huge explosion or a funny joke. (Hercule's ultimate attack) i would love to see a small cutscene of Naruto's Rasengan during a fight.
Full character transformations. the reason i say that is because in Battle Staduim D.O.N. the transformations would give you a boost but would only last for about 10 seconds or less making impossible to actualy see Super Saiyan Vs 4 Tail Kyuubi. so i would like for the game to allow all of the characters transformations and for them to last through out the battle or until the character runs out of power and reverts.
But this is all just my opinion of what i want to see. whats yours?