Honestly I feel like you should probably just flat out make a Disney fighting game if you’re so opposed to the KH original elements,
I'm not opposed to Sora, Riku, Kairi, Xehanort, Terra, Aqua, Ventus, heck even Eraqus. They're cool and fine. Plus I want the Final Fantasy stuff. I'll even throw in Roxas just for the fans. I just HATE Organization XIII.
Playing Birth By Sleep I've learned something else that makes me hate them even more. Most of them are originally from Radiant Garden. The stand-in Final Fantasy world! They should have been Final Fantasy villains. Then at least it would have been interesting to fight them and they'd have unique personalities and designs.
Seriously. Keep the Nobodies angle. You can even keep the kings of white bread toast known as Roxas and Ansem. But then have the rest of the Organization all be nobodies of Iconic Final Fantasy villains from the (convenient for the number of organization slots left) eleven main games that existed at the time.
But anyway. I'm fine with KH's original stuff for the most part. I just really don't like Organization XIII and it's making this roster annoying to make in my head because people would give me **** for leaving them out and there's ****ing THIRTEEN of them! That's thirteen roster slots for thirteen boring black coated wastes of space. I hate them all so much.