In California (one of the few places that's issued an L3 permit) the regulations place all of the requirements on the manufacturer. There is probably a workaround where the sacrificial company "installs" the self driving system (i.e. plugs in a USB drive) but then they would be the manufacturer and get saddled with tons of other regulations. Just for L3 driving alone they would need to get their own permit and their own proof of insurance or bond worth $5,000,000. Even then IDK if this would work given the department has a lot of leeway to reject applications on the basis of risk to public safety.
https://www.law.cornell.edu/regulations/california/title-13/...