Bush should replace Cheney just for the shock factor. Replace him with Mark Levin.
Bush is the de facto head of the Republican party. If he wants to steer the party in Mark Levin's direction, it could be done by tomorrow. But Levin isn't a declared presidential candidate so it might be a waste of paperwork and time, so it would REALLY mean that it's the direction Bush wants the party to go. Is there any indication that that's the direction Bush wants? It would be news to me.