Comments
Based on the use case information, the Person resource appears to be designed to solve a problem that is likely shared by many resources. If a system is trying to aggregate data from multiple FHIR servers, they need a way to link equivalent resources together. Is it really appropriate to make Person as a one-off mechanism to do this instead of having a core infrastructure to allow a resource to have a "link" to "related resources" and/or alternative URLs?
Note, this comment presumes that systems would not have any real need to link together differing resource such as linking one Patient with their equivalent Practitioner record.

Grahame's Comments
Have to think about this one; this aspect of aggregation hasn't come up before. Persons certainly get special treatment, so I suspect that they;'ll get special treatment in FHIR too, whatever we do about the aggregation question generally. Need to do research into this; what has the balloter done about this before?