That doesn’t do anything except let the taxi go out of service until someone cleans it - assuming that it would identify vomit without waiting for customers to complain after they sit in it.
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.
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