It it always a pain to re-configure the phone templates after an update. I would suggest to do this that way: Have a file for custom settings. As soon as there is an update, it will be downloaded and afterwards the settings from the custom settings-file will be set on the default template. (Default Template + custom changes file = custom templates). That way noone needs to take care to new updates, as their settings will stay active. For troubleshooting because of custom templates it may be an option to deactivate the custom settings-file in the management console. same could be done for other templates.