Create a NBU Vault Policy without a TLD being defined.

The other day, I asked how to create a NBU SLP so I could use Data Domain Replication to our DR site.  The answers I received were most helpful (even though Symantec has yet to mark it solved).

In doing additional testing, a NBU Vault policy works much better than a SLP in duplicating Data Domain data to our DR site.  Since I already have a TLD defined, pointing NBU Vault to another storage unit is no big deal.  However one day, I will be getting rid of my TLD.

So the question is, if doable, is how to create a NBU Vault policy without a TLD or how to create a virtual TLD.  Presently mu Master and Media Servers (2 out of 3) are virtual.