Agreed. I think what we have seen in Kentucky and Georgia is the model they will follow along with fighting mail in ballots. As
@Organic Potatoes said above, it is going to be very hard to move the election as Federal Law stipulates the EC must meet on Dec 19th. Plus, the election clause of the constitution makes it pretty plain that states get to determine the how, where, and when elections take place for senate/house, so unless they try to decouple the elections from one another I do not think you are going to see any real move to change election dates. This goes double for stopping mail in voting. I don't see how Trump stops them as the only way the federal government can interfere is with legislation, and there is no way the house is going to go along. My only worry is the courts, especially since McTurttle has spent the last 4 years packing them.