You don't need DNS to propagate across the WAN. Just set up your own root server. You'll have low-enough load to set near-zero TTLs (or just have a single root

You don't need DNS to propagate across the WAN. Just set up your own root server. You'll have low-enough load to set near-zero TTLs (or just have a single root server which everything uses). Although I admit I don't know enough about your use-case.