Where along that spectrum will you draw the line? Is that even possible to describe without being needlessly cruel, like someone who lost the use of both hands due to a stroke is killed but someone who lost the use of one hand and one leg gets to live?
These sorts of decisions should be left in the hands of those who are most impacted by it: The person in question. I'm a supporter of more dignified end-of-life options, of people being able to opt-out of life-saving treatment if they think it's not worth the fuss or the outcome is undesirable.
There's still a huge difference between someone electing to die with dignity because their cancer treatment has a 10% chance of delaying the onset by a few years, but a 100% chance of making their life a living hell for the duration, and someone who's told they're too ill to live and has their life abruptly terminated.
I wouldn't want to live on life support. I'd rather my wife/kids get a nice (well managed) trust fund for the remaining savings and just go in peace early.
Enjoy your manadatory execution when you're forty you old bastard.