I have never heard anyone rational, even in pro choice forums, say it should be a free for all. Put age limits on it since children have developing minds and lack the perspective to make such choices. Put awareness/rationality checks on it the same way we do any other medical procedure with informed consent. Unless the person is being purposefully isolated and kept from others, which is an edge case, I don't see a scenario where an invalid would be unable to find someone understanding to assist, thus the fear of being "forced to kill" FUD I hear often isn't realistic.

Obviously the best thing to do is to minimize the numbers of people who end up in such situations by addressing root causes. But that is something society has proven unwilling to deal with at scale. There will always be some people who have intractable suffering, with no tolerable outcome possible, and they deserve a peaceful way out.