I think the original Post was a good one; it covers what I would suggest, cryogenics and spray-on coatings. I had my brake rotors and drums cryogenically tempered. Parts are cheap? For double the cost (less saved labor) I should get 2-5 times the service. I don't have any experience with aerospace coatings, but anything that manages heat and friction should probably be considered. Also lots of parts are available in different grades; e.g. stranded vs single wire throttle cables. Low rolling resistance tires and aerodynamic improvements will make each of those million miles more easily obtained.
Some years ago Mechanix Illustrated, or someone, ran an article on 'How to make your car last forever'. I don't have a citation, but the gist was manufacturers economize on certain things like hoses, and uprating them will help.
Since the record is
more like 3 million miles, you goal is conservative. According to Wikipedia, rust (which never sleeps) is the biggest hurdle. See
Car longevity - Wikipedia, the free encyclopedia.