A Different Mugen

Is There A Mugen System That Can Allow Someone, I.E Me To Create A Platform Game Utilizing Components From Other Games Ex. Sonic And SuperSmash Bros.

I don't think so? The only thing I can think of is if you started game hacking, which I think is somewhat illegal?

So far I know that you can make your own fighting game with MUGEN with many different characters in it. You can create your own characters and stages, but it's only for the fighting game, not to make some kind of platform game or so.

I have seen a bleach-style fire emblem, and have been wondering about if it was real....anyone know

I'm sure it's possible, I've seen shmup versions of Mugen before. You'll just have to do some searching on Google.