Where should the TMSXE 3.0 server be located? TMS side or Exchange side of the deployment
The TMSXE server could be located anywhere where it can reach both the Exchange CAS server and the Cisco TMS over HTTP(s).
Are there any latency concerns we should be aware of with this model?
No, Outlook booking is asynchronous, latency won't matter.
Is an offsite hosted Exchange solution supported?
Such deployments have not been tested by the Collaboration Infrastructure BU, and are thus by definition not supported. However, as long as you are allowed to control the throtteling policy on the CAS server, I don't see any reason why it shouldn't work. But note that you probably won't get any assistance from the TAC in case the off-site Exchange solution breaks TMSXE.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.