I like your point about in-car leisure. As autonomous driving unlocks it in a new way, I would expect our for forays into autonomous vehicles to attempt to highlight the luxury of this. It certainly seems more appealing than tightly gripping the arm rests while you observe how the robot is doing.
I would add that interchangeable parts are probably not going to be a focus. The auto industries are pretty efficient at managing large supply chains to service several different models. If convergence was economically important it would happen more often.
More so a convertible interior than interchangeable parts. As with how RVs convert dining areas to beds, or how an SUV's rear seats fold down to provide more cargo space.
I think a comfortable, self-driving car would be a quite pleasant alternative to flying in many cases, especially if you're likely to be hiring a car at the other end anyway and have a good amount of gear to stow on a trip.
I would add that interchangeable parts are probably not going to be a focus. The auto industries are pretty efficient at managing large supply chains to service several different models. If convergence was economically important it would happen more often.