Yeah, this one is tough. You have a kid with a low ceiling, who just won you your first Big Ten title in two decades, and a much higher ceiling kid behind him. In the transfer portal era. Granted you need a first two games set up like this to get away with it, but I think what Harbaugh is doing makes WAY more sense than having them each take some series during each game.
Hell Lloyd Carr struggled with this 25 years ago, when there was no portal, and the upperclassman "program guy" he was trying to work in was Tom f'ing Brady