Modifying these services on the CUCM itself is not possible, however it is possible to create your own IP Phone services that duplicate the functionality, change it, extend it, or do anything you can think up.
You will need a lightweight webserver and some light web development knowledge. See the Getting Started section here:
http://developer.cisco.com/web/ipps/home and download the SDK from the documentation area.
Alternatively, for a more drag-and-drop development experience, the Cisco Unified Application Environment (CUAE) makes it easy to develop powerful IP Phone Services as well:
http://developer.cisco.com/web/cuae/home