Would it be ok if we have a sorting system in which we can filter each fighter by type

For example, Goku is a brawler with ranged ki attacks while Sonic is a speedster. With a sorting system this would then allow players to find a character quickly instead of endlessly scrolling through.

Would it be cool to have water for some characters to swim in or rocks that some fights can jump off of?

Super Buu is much more playable as he has more forms. Kid Buu is a bit easier to make frames for, but lacks enough screen time in the anime.

And how much can BASTON handle in terms of character animation frames?

The run animation is smooth as it could be.

Thats actually better looking with the body not posing in a certain way.

You could just slim down the torso, that way his body won't look like this

Still too chunky looking. It would make sense if it was All Might, but Izuku is a bit scrawny.

This one looks too chunky. Try slimming it down a little to be accurate. A few other areas could use some tweaking.

I can give you a few pointers such as using some images as a reference for certain attacks

Here is a more improved Ace with a much more accurate design.

Does he turn into a slice of cake or is he moving so fast he looks like one?

Smooth animation. The addition of in between frames allows the character to move at such pace.

I'm willing to improve your Scout by adding some balance to him as I see a lot of areas that need tweaking.

Question: Is there a character customization feature available in game or is it planned?

I see the Luffy sprite in fighting pose.

Overall a very good design thus far.

Looks better than before, but needs some fixes.

Luffy does not wear pants. His hat can be adjusted to show the red cloth around it. And the shoulders are too close to his head.

The legs on the sprite look too chunky. I do not see any sort of visible hair. His shoulders are too hunched up.

I suggest you focus on making his attacks short range in animation since there is no hitboxes that you can add. Also what arc are you using?

After looking at your pack, I've noticed a lot of missing animations to characters, preventing them from standing out. I'm willing to edit some characters while crediting you for making them in the first place. Your backgrounds are decent for a fight scene, but might need some polishing to improve.