Batman737
You need to take on board that the reason that it is not done, is that it would not be a foolproof way to totally stop the possibility of death by pilot.
The best you could hope for would be a 3 pilot crew, but since 90% of civil flights are 2 pilot, it is immediately obvious that the global airline industry would come to a sudden halt due to insufficient manpower. It can barely cope with the low pilot numbers right now.
It's also worth noting that out of those 3 pilot operations the 3rd pilot is often asleep in the crew bunk. Getting necessary rest so that he can safely operate the aircraft.