Your Question
I do not think it can be done with a few button clicks.
Unlike the AR3000, the 2000 cannot be reset to defaults. Even the AR3000 has to have the top case removed to get at the re-set switch.
As far as I know, to wipe all the frequencies you will need to do a full manual re-set, and that needs shorting some pins on one of the boards.
How to do that is described in several places. I imagine you have searched 'AR2000 reset' ?
Your decision of course. I would hesitate to do it I must confess. Presumably, bit by bit you will be overwriting the present frequencies.
Cheers
(Hopefully now I have posted this someone will come up with an easy answer and prove me wrong, lol)