Handle 10 remote locations

Hi,

What is the best way to handle NT Domain setup for 10 remote locations all over the world:
Either use several BDCs over WAN OR Use CITRIX (virtual desktop for remote users) ? Or there is another way ?

The users want access to MS Office 2000, Exchange 5.5 for Emails, run latest service packs & antivirus patches.

I have to take care of many issues like licenses for all users/software, upgrade systems, keep them running ship shape for 24×7 with minimum downtime.

Akash