Changing the Base Key registration of a BIG-IP

Just follow the instructions http://support.f5.com/kb/en-us/solutions/public/7000/700/sol7752.html

As long as the new base license has the licensed features (or more) than the old one, it will retain it's settings. As mentioned in the instructions, you may need to enter keys for additional modules (at the same time as entering the new base license) if you not using bundled modules.