WCA proposed reforms

Bit hypothetical at moment but assuming the govt adopts a similar approach to the last govt, in reforming the WCA to force claimants with various health conditions off ESA SG or the UC equivalent, especially re muscular skeletal issues and mental health issues, does B and W think it lawful that the DWP could just take a list of all those on their systems who have these issues and say ok, you are no longer entitled and must claim the UC as jobseekers now? Or would they by law need to actually re assess those people with a fresh medical under the new WCA rules first? This concerns me a little as I wonder if DWP might use this to just force ESA claimants onto UC in a purely administrative way, thus stripping such claimants of transitional protection as they would have to claim UC due to the change of circumstances such an administrative approach would cause. Or would this approach likely be unlawful?