As long as you have the permission of the remixer, sure. So say if I wanted to remix torachan's remix of one of my fics, I'd be fine because he's offered his fic for remixing. If I wanted to remix argosy's remix of my fic, I'd have to ask her because she hasn't signed up.

And it's not a silly question. In fact, remixing something that was originally yours and then remixed is kind of a cool idea. :)O