Pilots spend an insane amount of their non-flight time in simulators doing this very thing, to the point where when things do go wrong they subconsciously know the routine to address it. There's no time to think about a reaction in many cases. And now they want to just have one person be at that alert level all the time.
And I thought that fatigue was an ongoing problem with pilots now, but I'm sure having just one person focused the whole flight won't hurt.