"There is a related and more difficult question. Can a person, while conscious, give advance consent to sexual activity while unconscious? The Supreme Court of Canada has answered that question in the negative, and by doing so has potentially opened a serious can of worms."

You raise a valid point in my view, W w. In effect the SCC has restricted the rights of everyone, with the intent to protect a very small minority of cases. There is a parallel to your point in the area of assisted dying, wherein advance directives aren't permitted in cases where people may be in a coma or suffering from dementia.

In my layperson's view, the SCC must apply all the usual criteria before limiting the right of a person to give advance consent to sex. It's hard to see how that limitation passes all the Oakes tests.