You have to sign the same waiver when an MD does surgery, and you still get sued! It happens even for elective procedures with less than perfect results.
This subject is close to my heart and livelihood. Don't tread on me, please. I know enough about this to curl your hair. If what you propose were actually done, the PAs and nurses would be back working in the hospitals and MD offices in about.....two months, and damned glad to be there!
The whole point is to bring the free market to bear on the problem in every way you can. Anytime you can increase supply, you'll decrease demand.
That's probably true somehow in the legal area, too.