> In either scenario, the administrator is going to need to keep a mapping file. Either remoting node identifier to transaction manager node name (my preference) or EIS name to EIS int key.
That's not quite right. EIS names are scoped to the node and the mapping can be maintained programmatically by e.g. the JCA xa recovery plugin registration code. The nodeIdentifier is potentially enterprise (or at least data centre) scoped and needs manual coordination and maintenance or some centralized/hierarchic registry service to manage uniqueness. Than again so does allocation of a uniq string node name in the first place.