So you could get half-way there by just sticking an XML file on a local HTTP server and point them to that. You would be able to configure probably 95% of the settings in a common file and then manually go through to update the programmable keys and SIP registrations as required.

If you have the internal resource to do this then it isn't a terrible solution. But it is where you can come unstuck when wanting to "push an update" that. But again, you will probably find that a hell of a lot of the settings will be common across all the handsets.