Your project will be a ton of work, that's for sure. You're planning on making Flea, Ozzie, and Slash player characters, is that right? Lots of new sprites would have to be created for that to occur, unless you want to make do with what already exists (Slash has a very full sprite set already, but Flea and Ozzie are very limited IIRC).
Technically speaking, given what Justin3009, Azala, and probably others have done, this project should be possible, as long as you can make the sprites.
