If its a secure network then I would not like to see that a request even might get announced towards the internet :-)
Btw, you added the local IPs which each VCS shall handle to its local sub zone?
I do not think that the peer setting is a good idea. I do not think that both peers would be queried at the same
time anyhow, would assume it does some load balancing, but never traced on that.
No chance that they just register to the VCSs internally? If they roam you could still use some
split DNS so dependent on the network where they are in they hit the fitting VCS-E.
Maybe an IPGW in each segment can help you as well.
The systems which are dialing up these ips are able to dial e164 numbers or uris right?
Maybe you could introduce a number plan which maps a number to an ip address.
If the ip address is something like 188.8.131.52 you could dial 001002003004
That's easily done with a regex.
I just tried to make me an alias 101 and made a lookup on the dns zone for an ip.
Dialed the alias and got connected to the IP, so that shall be doable.
Anyhow, as this is a special account I would talk to a Cisco engineer and ask him for help.