Thanks for sharing what happens later. I completely understand your viewpoint. I would love to see Miyuki in that state as well, but it is bound to become monotone after some time. She doesn't need any redemption arc, or any arc, to be honest. Just allow her to leave this story and be forgotten once and for all. We tend to wallow over the fact that we don't get to see the future of certain characters in other series, but for this one, I'll be glad if the author forgot about Miyuki and didn't mention her ever again, except for maybe just a footnote at the very end.