The sensors can always fail, even multiple sensors will fail in the same way sometimes (icing.) You have to make sure that when they fail, the plane degrades gracefully and predictably rather than pointing its nose at the ground. I seem to remember that some European guys were working on such a concept, whatever happened to it?
It occurs to me that all of the solutions that Boeing is now proposing (to a problem that they still have trouble admitting exists) were solutions that had to have been considered and discarded during the initial design of the MAX. They have proposed nothing that would have incurred any significant cost to the program, so why is this new way better? We are now trading out false activation of MCAS for false deactivation, and if MCAS was so important that it was worth the 346 lives lost why are we so casually disabling it? Remember that Boeing told the American President that the plane was perfectly safe after the second accident.