It's an interesting point you make, and I have to say I definitely agree with your assessment of the importance of Captain Kirk's profound philosophy, "I need my pain!" So true!!! In fact as a side bar, as an artist, every time I go through a painful episode in my life, that's when I have the best inspiration and the most productive period of writing. I've always joked that if I were constantly miserable (or "in pain") I would be an artistic genius, but it's my relatively normal life that holds me back. Lol And there's some actual reality to this too. Think of all the brilliant artists in our history, most of them suffered from some sort of debilitating ailment or emotional pain. Beethoven was deaf by the end of his life!!!
Anyway, back to the point. I understand what you're saying about having the right to suicide versus artificially "dulling" the pain by having an assisted suicide. However, Putting it crudely - at the point in which you cease to live all physical pain ceases as well. It doesn't really matter whether or not you do it yourself or if you have someone else assist you to that end with drugs. For the individual the result is the same. And honestly, if you put a bullet through your head, you're not gonna' feel any pain either - the death will be pretty instantaneous. There are some other ways that people kill themselves that I'm sure would involve a lot more pain, hanging yourself, slitting your wrists. But you always have the choice to choose a more instantaneous method.
So I wonder what they really mean by "Mercy Killing"? Who's the mercy really for? My sense is that it's more for the family than anything else. I would imagine that it's pretty gruesome and traumatizing to witness the aftermath of someone shooting themselves through the head, or hanging themselves, or jumping off a building. So in that regard I do agree with Kevorkian's method of having it happen in a controlled, planned and dignified fashion. I'm sure the families that support this action by these individuals have felt a lot of pain, and will continue to feel the pain after the assisted suicide; ideally they would have sought counsel or therapy to help them through making this sort of decision with the individual. But in the end you're saving them the trauma of witnessing the violence of something like a gunshot to the head or the anxiety of not knowing if the overdose of sleeping pills will actually work.
So in that sense I don't totally agree with the problem you have with "dulling" the pain so to speak. I'd like to believe these people and their families don't make these decisions haphazardly, (then again, maybe they do), the pain is there for them to feel. I think I see it more as he's eliminating the trauma of the actual event itself.
I will say though, of what I remember of the controversy, the argument he made was one of easing the pain of the individual, so in that regard I think your point is correct. However, I think he was perhaps doing the right thing with the wrong reasoning.