I will only add to what Mr. Potter has said.
Even today, when it comes to advance directives, which in many cases are much less significant in their consequences, they are mainly distinguished from an advance request because they are only about the withdrawal of treatment.
The systems within provinces and territories, within institutions and across the country are not only diverse, but they are frankly not all that functional. A request that may be MAID, or a directive that a person may file in the context of their interaction with a family physician, a visit to a hospital or whatever, may or may not surface again on some future occasion. There would be an enormous amount of work to be done, not just at the level of the legislation and the permissibility of such a regime in the Criminal Code, but in the actual implementation within the health care system.
I'm not offering an opinion about whether or not advance requests should be permitted. I'm just commenting on the infrastructure that would be needed, including, for example, periodic renewal of the request, so that any last request that is made is as proximal as possible to the point in time when the person has identified that they would like that advance request to be acted on.