I don't know how to answer you, other than by repeating things I have already said. Even the Supreme Court observed that vulnerable persons were at risk in several ways. For instance, people could ask for physician-assisted dying because someone in their family pressured them to do so. Or, a vulnerable person may not have access to other care, or was poorly informed on the state of her health. It could also happen that her understanding has been compromised by her mental state. There are several circumstances where there could be doubt as to the real wishes of a person who asks for physician-assisted dying.
In order to avoid blunders, abuse and errors, you have to put careful thought into what the risks are and try to find answers to minimize those risks. Generally speaking, that will be the objective.