My seats?? Noone owns a self driving car, you rent one when you need it. As for the fleet owner, I bet they will solve this in any number of ways somehow including the risk in the cargo fee
I predict plenty of people will own self-driving cars, at least at first. Habits don't die easily, and car ownership is seen as a key part of independence and self sufficiently in America. Some people will want to own them, whether or not it makes sense.