This is a very interesting discussion. Bert brings out some great points. I think this subject could be a great breakout session at the next user meeting.
Amazing charts moves a whole lot of data across the pipes and I suspect a little VPN connection would not work well.
If Amazing charts wanted to support multiple offices on one database they would need to create a group within the company to support this and price it higher. The competition is fierce and might distract from Amazing Charts core users.