This fear that we're going to end up with Michael Carrick permanently seems to me a weird mixture of wild optimism and abject pessimism.
By all accounts, Carrick and McKenna has had key roles in deciding our setup, as well as in training. They've obviously had the trust of OGS. It's really hard to believe they have excellent and fresh ideas that have not been implemented solely because OGS has blocked them. Or that having them and Phelan on the bench would give the players a boost in confidence. Rather the contrary, really. So my baseline expectation here would be that we're going from abysmal to worse in the games ahead. I suppose you could hope for a temporary lift against Villarreal, as the players respond to all the hullaballoo of Ole's sacking. But that's hardly a cert either, and is unlikely to last. So why would this setup work any better than it already has, and why would you think Carrick is going to do well enough for that to even be an option? If he can bring us back to something that resembles basic functionality, he'll have done more than you could reasonably expect. And even with this board, suspecting that that will land him the permanent job is probably to expect them to be even more incompetent than they actually are.
My primary worry is that we'll simply carry on being as bad as we've been the last few games, until a proper caretaker is in place.