As far as the WAN response times, I've only ever encountered a direct reference through the seminar classes - taken with a grain of salt. It really comes down to MAPI and the WAN protocol - they don't like each other. However, here's their performance documentation and white paper, concerning users, connectivity, etc.
http://www.blackberry.com/knowledgec...97690&vernum=2
Typically speaking, I think that response times should be within 50-70ms at a maximum (obviously preferrable would be under 10ms). As for users, they claim 2,000 per server, but most people on here will either branch off with more BES servers when they start experiencing issues, or they will simply call the magical number between 200-500 users - I'm not sure if many administrators on here actually practice maxing users at 2,000/server (once again, this is a MAPI performance issue).
As for the services being installed in the remote offices, I do not believe that is necessarily what the functionality behind the remote installations of the Router/Attachment services is for, to be perfectly honest. You can only have one Router service per BES, I believe (someone can correct me if I'm wrong though)...