Have you thought about writing a transformation story from a perspective of some unaffected person? For example a woman whose husband is changed, who usually would conveniently disappear in the story. Or perhaps do you know of some stories with such elements?

I’ve read a few stories like that, and that theme pops up in some of my stories, although usually the narrator is being changed as well (as in Letters From Prison). I’ve never been a huge fan of these kinds of stories myself, because I find they tend to unnecessarily obscure the change, so I usually avoid writing them, and none really spring to mind as something I would recommend–sorry.