Ok I’ll give you that, but whats to stop them from double dipping? What if the car had FSD already and they dumb it down to AP for you to purchase and pay for FSD again later?
would you buy a BMW m3 Chassis with a 328i motor and upgrade to an m3 motor again later?
So, going back to my floor mats example. Let's say the person who bought the car new bought floor mats. Then, you go to buy that care as used, and the dealership lists the floor mats as optional. How's that a problem?
The whole point of selling used cars is that someone pays for something that's been paid for previously.
Heck, when you buy a brand new car from a traditional dealership, it's already really been paid for at least once already - the floor plan financer for the dealership's already paid for the vehicle in-trust.
So not sure why you're hanging up on FSD. It's up to Tesla if they want to sell that option or not. Makes absolutely no difference whatsoever whether it's been paid for by the last owner or not.
(And to answer your question: No, I wouldn't buy a BMW chassis, even with someone else's money.)