Didn't think my comment on another thread would inspire someone this much. ^^
But yes, like I mentioned there, a Monster Polymorphs would be a neat idea to add for Halloween events just for the fun of it.
And my vision of it were that it would have the limitation that you can't do anything or the effect will wear off.
But ofc, it possible they could add some zero-potency abilities just like some mounts have for visual flavor.