Personally, I'm always hoping for a story like this to have the changed character really start interrogating who and what they are now. both in the sense of "well I'm not actually human anymore, just assuming a human shape when I'm not in my true form" and relating to Gender Stuff.
There is tremendous introspective potential in a story where you are made fundamentally different, and your periodically appearing old self is merely a façade stretched over that, a lie to both others and yourself.
Sadly, most of the time the writers don't seem to actually engage with that opportunity.