It does one better, it holds the passenger who created the mess accountable for the cost and then drops them off the service. You get some bad actors, but you can quickly weed them out.

Doesn't change the service outage piece, but it will get better.

That being said, your key point - people can do what they want in this thing and no one can really stop them, does stand.

this is a trivial problem, same way rental car companies solved it:

  1. operator or computer vision detects dirt in salon
  2. route the autonomous vehicle to contracted carwash
  3. return car back to service
  4. charge customer for the cleanup