Schema wanted to support all of the document-centric stuff too. So you are willing to use an XML type description language that has a hard time supporting existing search technologies, and are willing to cut off a huge installed base?
The IETF has always favored getting a broader set of technology platform implementations of its standards over ideological purity--this doesn't sound like IETF-zen to me.
Simon St.Laurent "Every day in every way I'm getting better and better." - Emile Coue