you would do well to look up the reasoning being SURS - SID to UID/GID Resolution System. it sounds like exactly the same sort of thing is needed. draft-lkcl-sidtouidmap-00.txt what is _really_ needed is for Unix systems to adopt GUIDs or SIDs for world-wide user and group identification, rather than locally-applicable uint32s or uint16s that stuff everything up rather badly when it comes to very large networks.
NT is actually far better positioned than unix, due to its use of the VMS security model, to provide worldwide security.