Perhaps an adequate solution is to use LSIDs and provide definitive guidelines indicating how they can be embedded in URLs so that we do not loose interoperability with the rest of the world?  This is probably much like Ricardo's LSID proxy proposal.  Except in my opinion it should be extended further to be a general GUID resolver to help resolve whatever form is used for GUIDs - then one could embed a handle, LSID, HTTP URI, FTP URI, LDAP URI, or even, for the ancients of the internet, z39.50 URIs in a resolver proxy URL and get something back.  The problem of course is that the content that comes back will be different for different protocols - but it would, I suspect be possible to provide a generic form of metadata for the different protocols.