I'm old enough to remember when the pages of "Flight" were full of navs ,radio ops and engineers using exactly the same arguments now appearing here.
The bottom line with removing all the other crew HH was that there were still humans on the flight deck. As an example of how a third crew member did save the day look at the accident of the Ansett 747 in Sydney. Despite the FE being confused about the configuration of the landing gear he was the one that prevented the flight crew from trying to go around after the T/R were deployed.
The challenge to the tech heads is can they guarantee that the software required to operate autonomous airliners will be 100% reliable and unable to be hacked into?