Despite my name, I am not a doctor
I will agree that there are bad doctors out there that are just prompted by greed. This especially applies to surgeons, IMHO. But I would say that there are more good doctors than bad doctors, though maybe that varies a lot from region to region. I think that the greediest people in medicine are the pharmaceutical companies**. They push their product which may or may not do what they claim, and in some cases the treatment may be worse than the disease. Think of a brand name drug, Advil, Tylenola, Aspirin. By law, generic brands (ibuprofen, acetaminophen, acetasalisilic acid) have to be exactly as effective as the same brand name. Now, when the general public is inundated with commercials for brand name drugs, they are going to think they work better than generic ones. If it is just something like ibuprofen, not a big deal. But for prescription drugs, the price difference can be pretty big. Even if a doctor suggests prescribing the generic drug, saying how it is just as effective, the patient may be convinced by advertisements that they need the brand name one. Hence why you will see a commercial saying "ask your doctor about...".
Another thing that I think is wrong with medicine is how litigious it is. I know personally of cases where doctors would not normally perform an operation or a treatment since it is unnecessary, but may offer it out of a fear that they will be sued if it is found out they didn't do every single thing they could do, even if it wouldn't have made a difference. But I will concede this is true for the reverse, where a patient does not want something, but is pressured into it by the doctor.
I guess the point of my hypothetical review board would be to make sure their reasoning is legitimate and they understand the risks. But like I said, who is to say what is legitimate? It's just that people sometimes get confused in hospitals and only want to get out, so they might sign out AMA without fully understanding.
** Of course the REAL greediest people are the insurance companies, but that's a whole other can of worms.