Neverthrive said
It would be really cool to include everyone but… that’s not very likely considering the work load that would put on the very small production team. Honestly though, I feel like a fighting game should never have a roster that ain’t in the double digits. Maybe if some of the characters or sprites, or whatever, were to be palette swaps and clones, sharing most moves, animations, whatever (probably still give them their own finishers if that is a thing) then more characters could potentially be fit in. But I would think most people would want to be their own person. 
If this is going to happen, and I hope it does ’cause that’d be fucking awesome, the first thing we’d need to figure out, I think, is what number of characters is actually feasible to program and animate, and then to figure which people are going to be included in that number. Then, I would suppose I would need an idea of what people would actually want their characters to be and then I guess I would do my part.  

Something like where you custom design your character when you first play it. Kinda like when you design your Xbox avatar or something. Then you get to start applying fighting styles, moves and attributes from a pool of attributes. Maybe you start with a limited number of slots for those to fill. Then once you have created your character, you can start fighting.