I'm glad you brought up system redundancy 404! Manufacturers have been simplifying and integrating redundant systems. We are flying with less hydraulic systems, less mechanical systems, less engines, less crew. There still is redundancy, just increasingly less of it.
Parabellum, your HKG bound pilot will have had 6 hours rest, because they actually had 12 hours. Your abnormal situation will be monitored remotely. If its more serious than that, then the Captain will be doing the same as what happens today - and not get much sleep. (I'm only half-serious) The reality though, is that your 4 crew operation will become a 2 crew operation well before it's single pilot...
The military are well on their way down the automation path, and that is where most technological developments are incubated - and proven. Auto-airliners are a long, long way off, and there are plenty of steps along the way: Semi- and fully-automatic surveillance, automatic go-arounds, automatic and dynamic normal configuration, increased automatic abnormal management, fully-automatic asymmetric flight. We're a long way down many of these paths already.
In the crossover though, I think the greatest risk is from complacency. System capability isn't inversely proportional to skill required.