I wasn't able to achieve this. How'd you do it?
My Kemper never let me erase the "final" Rig, so I keep a default one in it (Burns' RR Rig from the Exchange).
I just select the rigs in RM and press on the PC.
How are you trying to delete it? In RM, the KPA or either? Are you seeing that final rig in RM as well as the KPA? You're not getting the damaged rig message in RM are you?