Wow! This started with an idea about a single pilot watching the office in the cruise to a single pilot, even pilotless, airliner. That's quite a leap from the opening topic.
Some years ago, in Italy, and I suspect it still exsits, FTL's were 16hours for 2crew & 24hrs for 3 crew. Why so long? This is UK heavy crew duty times for only 2 pilots. How can 2 pilots be expected to stay alert for so long? And this was planning; the question of discretionary delays was a very open one.
The answer! The Italian CAA considered the autopilot to be an extra crew member. Thus on a long-haul flight of 13 hours stick time at night, and after 6hours time zone, it was necessary to combat ZZZ. On a NAT Track this was not too bad as it is +/- 1.00 between checkpoints. However, if the other bod nods off it could get interesting. The C/A's were still dinging every 20 mins to keep you awake. Bl%#$y nuisance. SELCAL: sometimes did the same.
Where it got interesting was on multi short sector days as the FTL's did not reduce as sectors increased. Then the concept of the A/P taking the strain into non autoland airfields was non-sensical.
The point being that some CAA's might have sneekily being doing this for sometime without being open about it. It was all about human stamina, or lack of, and more faith in Honeywell & Sperry than el Commondante.