A recent poster said she didn’t expect that recognizing the number of people in a car will be difficult. While I broadly agree, I do think car manufacturers are going to have to at least attempt to defeat “mischief.” Maybe it’s my all-boys teams growing up, but I think on most teams at least one guy would have tried to sneak into a cheerleader’s ride home if he could get away with it. Some sort of virtual turn-style would be required.
I really must thank the commenter because it made me realize the unique expectations of different buyers. For example, today if you have 3 passengers to haul, you probably get a minivan. Features tend to be a matter of preference and budget. As vehicles become more capable, their features will become more customized. This may include requirements for more cameras, or storage space for an office, or more range to permit uninterrupted meetings.
Currently, 90% of a car model is the same, with minor details being added as requested by a customer. Software/Firmware may permit a substantial amount of customization that will make a vehicle seem highly tailored, but still not require a long lead time. In the future, it is entirely possible that a firmware/software/app upgrade will provide a new feature set to meet new customer requirements.
For example, if you start to have a need for your car to deliver you children places, you may download some app that would include facial recognition. The cameras themselves wouldn’t change; the data processing and user interfaces would. On a tangential note, even the ISS deals with software and firmware patches.