Ian W
Very good post.
I agree that the challenges are not technical.
The problems are in certification, legal issues plus public perception.
The thing that will have a very large effect on all these areas is the current nascent autonomous cars that are starting to appear.
The legal issues are the same even if different in scale. Who is responsible if it crashes?
The certification, the same. I think the thing that will happen is that the military will fly transports around autonomously for a while, and as evidence mounts for their safety advantages, the certification industry will be forced to evolve in the face of evidence.
Whether you understand it or not, safer is safer.
I think once people get used to their cars driving them around, the plane is not such a stretch...