Seems to me like a bunch of hassle for too little use.
I would say this because IMO it would have to be limited heavily. You shouldnt be able to polymorph your friends into gigantic everything and have them walk through areas.
You also should be able to turn EVERYTHING into a rabbit and walk through areas
So, it would be limited to only a few mobs being able to turn into a few things. Not enough for the coding IMO. I could be viewing it wrong though.
Ah well