Admins and users can easily make button changes to phones without making a new template. In EPM, Global Settings make sure ‘Admin UCP’ is enabled. Then browse to EPM, Extension Mapping. Each configured phone will have a button at the far right, the tool tip says “UCP Custom Entries”. You can use that button to make changes for that one device, or reset back to template defaults. You can also grant permission to your users to do this themselves in UCP. https://wiki.freepbx.org/display/FPG/UCP+for+EPM+Admin+Guide
That’s pretty cool Lorne! Don’t usually deploy UCP widely as most users are scared to death of messing with things so haven’t looked into it really heavily. One or two power users per site usually is about it and that’s usually for general voicemail access.