You could add men in power suits with upgradeable modules, that enable speed upgrade, reaction upgrade, power upgrade, upgradeable augmentations for different things like predicting opponent's next move, bullet time, each character's suit could have unique abilities like throwing solid projectiles, spewing acid, telekinesis, supermagnetisn.

A sort of story mode could be added where a character moves through a world and encounters opponents to fight intermittently.

It's not a bad idea. It could work if I can have it fit in with the themes of my game.

Speaking of themes I have characters that are sci fi-cyberpunk style, some medievalish fantasy styled characters and some horror based.

Now would I be better off combining all these characters into one themed genre? Or would it be best that I separate them into three different fighting games? One sci-fi, one horror and the other game fantasy medieval magic-like?

I think it's better to combine them, given that the fighting genre normally consists of a not so large game, and it will give the player lots of variety.

I would love to combine them all. The problem is I have about 22 horror-styled characters, about only twelve sci fi-cyberpunk based characters and only about only 3 fantasy medieval-magic based characters which makes the scale uneven compared to the diversity of characters of each genre type which may upset players 

Are there any other inspirational ideas I could work on that are sci fi-cyberpunk based and medieval-fantasy like that I can add to my list and work on? Anything that will help with cyberpunk and fantasy magic based characters ideas would be very welcome and I'll figure out the rest,

Also since I have horror characters I wanted to add brutal finishing moves. I was intended to make them gory but since I might just combine the fantasy and cyberpunk characters together, am I  better off just dropping the idea? Or could gory finishing moves still work in this setting?

Thank you so much for your help.

When it comes to Sci-fi games, I love when there are moments of frustration; so if your game would have that kind of moments, then it will be more addictive in my opinion

that's cool...and/or right after a good hit, that small window of time opens up, the guy taking the beating is shaking off the last blow briefly and an opportunity to double damage or worse becomes possible. Anything that adds layers of interaction that aren't available from the base punch or kick. 

That's an idea, I could incorporate some heavy challenges and weaknesses for each characters. 

Thanks! I'll keep an update soon what I need help with.

Thank you for any feedback.

If you have any advice on some of my characters I would appreciate it, thanks again.

Which idea would fit best for the character's choices? -

A miner with pitch axe and sand power capabilities from somewhere underground Australia, an ancient Chinese emperor mummy with sand powers, or an ancient pirate with sand powers and cutlass saber sword, awakened on a Costa Rican beach?

A Celtic wraith with a claymore sword or Japanese wraith with demon katana?

Thank you for whatever help you can provide!