As any other server, if you change Universal IP, clients will not be able to access to it, so you will lose lots of capabilitites (not WDE, but passwords wont be synched).
Putting Universal in DMZ is ok. what do you mean by rendezvous timer?
This way, external users can log to web messenger
If you are concerned about performance, it would be ok, even faster than placed under internal network.
If you are concerned about security, you should place universal in internal ip and open port 80 (web messenger)