The FCC, under multiple commissioners appointed by vastly different presidents and approved by vastly different senates, for a period of over 30 years, has allowed Sinclair to openly violate the "no one company can own more than one of the big four in the same market" rule. So they should either do away with it or actually enforce it.
As to the no merger between the Big 4 networks rule, it does not seem to make sense to allow such mergers, IMHO. Everybody selling thing to the networks (studios, actors, sports leagues) and buying things from them (advertisers, and you and me via carriage contracts (which should be abolished, OTA TV should be free) ) would be at a disadvantage.