Unfortunately AXL does not support using the Universal Device Template. Certainly similar functionality could be achieved by programming to the existing AXL requests (<addUser>, <addLine>, <addLine>, etc.), however.
Yes, but the issue is I then have to worry about the Phone Button Template vs the Phone Model. The awesome thing about the self provisioning is if the phone doesn't support the universal phone button templates (8831 is a current model that doesn't) then it just creates an individual template. Using traditional methods i have to maintain a table of phone models that support for universal phone button templates and tool different actions for those that don't.