[Matrixbeast]

The problem with Fighting games is that you can't have that many characters. Notice how many of the characters in the Ultimate Ninja and Budokai Tenkaichi series are just reskinned versions of other characters. It becomes repetitive because so many characters are almost literally copies of others with one or two variations.

As a result, all the dark riders you want to include will literally be black repaints. Ryuga, Dark Kabuto, Nega Den-O, Glaive, etc.
Additionally, it cuts characters who are important to their series for unimportant characters (Zolda being removed in lieu of Ryuga, ANYONE else from Kabuto being cut for Dark Kabuto, etc).

You're eschewing character variation for character number, which is a poor way to handle it. Rather than have a group of, say, 25 characters (15 main riders, 10 other characters (Kaijin, secondary riders, whatever) who all play differently, uniquely, and with their own style, you're going for 130+ characters who will all fight in a similar manner with little variation and extremely simplistically.

I'm trying not to be negative, but that's just what happens when you go for quantity over quality. The characters can't be made completely unique because there just isn't the space to do so for each character.