That's an example that hits close to home as 2 close family members are Nurse Practitioners. This is a flawed example because Registered Nurses do not do the same job as a physician and are legally not allowed to learn how to do it. What if the nurses were allowed to shadow the physicians for 4 years? That would be called residency.

What if you have Nurse Practitioners with a Nursing BS, 4 years of nursing experience, a Masters degree in NP, and 4 years of experience diagnosing, managing complex conditions, etc.?

I personally know of several examples of Nurse Practitioners who are a drop-in replacement for an MD and that was achieved through work experience.