That is an interesting idea.
I'm not familiar with the story, me and horror genre don't mix too well. I'll have to look into it.
I think the main part that tripped me up, was that I was trying to come up with ways on how he could be the beast then be "human" again afterwards. All of them prosaic at best, some completely childish. Then I thought of him being entirely human, just his behaviour be beast like. The more I dug into it, it just put me off.
One draft, he was a steam powered robot.

Silly, huh?
If ever I pick up that idea again, I will look into the possibility of him being some kind of experiment.