Genghis,
Thanks a lot for taking time to share all these invaluable insider things.
Still, I stand that a thoroughly chosen relevant degree as a back up could be a very helpful matter.
Pilot job could end in a blink of an eye. Mainly for health reason. And all of a sudden you are nobody with no name. All the way from the helm of a superjumbo. It's not wise to miss opportunity to get proper degree if someone is able and willing to finance it.
The back up should be very practical, so that you can stay around it while flying. As I already mentioned: accident investigation, CRM, aircraft performance, general management and, as you mentioned, aeronautical/aerospace engineering. Looking for other ideas.
And, BTW, there is another real threat to the pilot job - automation. I'm pretty much sure in 10-20 years from now new cargo airplanes will fly without pilots, shortly after that followed by passenger aircraft supervised by a single pilot. Technology is already there. Implementation, testing, legal procedures will follow.
This should be a reason for very serious considerations in life and career planning. So, we are probably talking not just about back up...