You're right that the choice has to be an informed consent, and it has to come from the patient, not from the doctors. It has to be based on the situation as assessed by the person first, and then assessed by two independent persons, and maybe even more people.
You said that it's difficult to put a line somewhere. If you have somebody who is 17 years old, suffering from cancer, in terrible pain and suffering, and he or she is asking for access to MAID, you will deny that? For example, in some provinces, like in Quebec, at 14 years and over, they can decide to consent or not to medical treatment. That person could refuse to get another treatment and decide that they want to end their suffering. Will your deny them in such a case? Or, do you think there should be no hard line in such a case, so that we could say yes after properly assessing the situation?