I did some thinking and here's my result.
Store all players who have bunny ability to an external/other database.
This brings a factor: Ranks will never change.
Until the cvar changes ranks won't never change. Pro stats will stay the same.
You'll also get many data corrupts due to checking every round start if player is a bunnyhoper, freeze stats for one side and activate another. Merely ending up with unwanted stuff you have to face in the near future.