One way that you could make this work a little easier for you would be if you locked down client MAC address to host name maps on the main server, and only supply the locked down IPs from that server, and on the other server only supply generic IPs from a different range. The generic IP range could have a more restrictive policy in effect, so effectively they can only access enough to notify a sysadmin.
I've inherited a very similar setup, and this is essentially the method we use. Both servers have the same MAC->Static IP table, and either one can respond to a given request on the network. They also have a pool of "Roaming" IPs, with one server handing out odds, and the other handing out evens.

Matthew