YaUT - Yet Another Upgrade Thread

I have a GroupWise move/upgrade project in the works, and would appreciate any comments or suggestions. Here's the scenario: The existing GW system spans three physical locations, each with a single domain and PO. Total user count is about 200. All systems are running NW65 SP8 and GW 8.0.3. Let's call these locations A, B and C:

A hosts A-DOM A-PO A-LIB WebAccess GWIA (Primary domain)
B hosts B-DOM B-PO B-LIB
C hosts C-DOM C-PO C-LIB

The company is adding a new office, location D. Initially some (but not all) users will be moving from A to D. New server hardware has been purchased for D, so the intent is to make D the new primary domain, and to host GWIA and WebAccess from there. Of course I want to make the move to GW 2012 on OES 11 as part of this transition.

The extra fun comes from the fact that there is heavy use of DMS, and the document libraries are external to the POs as Novell once recommended as a best practice... ;-)

Can I simply install a new OES 11 server at D, join the tree, and install GW 2012 into the existing system? Or do I need to install GW 8 on the OES server, add it as a new domain to the existing system, promote it to primary domain, then upgrade in place to GW 2012?

There are fast, stable VPN links between the locations, so I'm not too worried about doing user moves for the people who are relocating. But what about the documents stored in the libraries at A, B and C?

Another possibility that occurs to me is to move the whole A system to D and do an upgrade there, then allow the remaining users at A to connect remotely. Eventually the office at A will be closed and all those users will end up at D anyway. Is there any advantage to this approach, which will let me do the tried-and-true Netware to Linux migration? (Yes, I have Danita's book!)

Thanks in advance for your help.