I understand you're using 4 of the most popular anime, no 5, but I recommend to add more like
1. Jojo's Bizzare Adventure (especially this one, I'm a big Jojo fan) (especially the crusaders, the Jojo's and Buccelati and his gang)
2. Maybe some guys from one punch man
3. Add like Madara or something
I'll let people who reply on this add more stuff, please, people continue this post, our goal is to make this the ultimate anime fighting tournament, give some ideas. Our goal is 100 Ideas I've already started on 3
oh wait I take it back there is a Madara now I'm only on 2 :(
But if you do plan on adding Jojo, I have a lot of ideas (by that i mean 2, but it contains a lot of text)
1. For Dio's "The World" he doesn't need the level up thing, he gets a rage bar. The more he takes damage the more the rage bar gets filled. and if it reaches a certain level, you can stop time, you can stop time and use road roller. During the regular time stop you can mostly do whatever you want, like punches and knifes but you can only do the road roller if you're on full rage bar and of course this road roller does so much damage.
2. For every character, there must be a little extra selection where, for example, Goku has SS, super SS and stuff, why not implement a little selection where if u select Goku you can also select the SS type, of course, I won't be saying this if it has no connection to Jojo, you can add a part 3 Jotaro, where his special ability is he stops for a few seconds and if the enemy attacks him Jotaro teleports behind the enemy and lands a barrage of punches (also known by the Jojo fans as "ORAORAORA barrage") there's also a part 4 Jojo who can stop time like Dio but soesn't need a rage bar, instead you can have the normal level bar. For the part 5 Jotaro who did absolutely nothing, I can only assume that he can stop time completely, but if he stops time he can't regain energy/mana/chakra whatever and the time stop will drain most of his energy, leaving him only enough for 2 barrages and a bullet throw before the player can decide whether to resume time or not.