Sounds like you're talking about making a fairly comprehensive framework which provides a very high level API to the end user. Or maybe you want just a loose collection of API's that play by the same rules? It would certainly be interesting, and done right might provide a mice basis for allowing people to leverage each other's work.
That said, what you're proposing here is hardly trivial. Were you planning on taking the initiative, or is this another "hey, it'd be cool if someone did..." idea that's inevitably easier said than done?
If you do go forward with it, I can provide C APIs for mp3/ogg playing (not winamp-control), and HD44780 based character LCD output, for now. Heck, maybe some people want it regardless?