AC Support pretty much don't want you using anything other than SQL Server 2005 Express. You'd need something like SQL Azure as a cloud service:
http://www.windowsazure.com/en-us/home/features/sql-azure/I'm sure MS will have no problem keeping their side active, but you always have to invest in solutions that will ensure your internet connection as well. Which will probably involve getting a T1 line at each office. Which are pretty damn expensive. 300-400/month usually.