Without comprehensive re-valuations any tweaking (or more) of the way in which Council Tax is charged will be storing up political problems for the Govt., although equally any process of revaluation is also politically fraught.
A astute political leader would grasp the nettle now & launch a major revaluation project with the expectation it would be able to be largely finished & enacted ahead of the next election.
But, sadly we do not have any astute political leaders!