I'm also considering Screech or Leer over Scary Face. More variety in what it can do with the flavor moves is always good. Now, this might sound contradictory considering I want three trapping moves, but those are all core to the design (and learning Bind and Wrap at once is very fun, at least in game).
I don't think you should add Screech instead of Scary Face. Remember how it can't use Hyper Voice? Same thing for Screech, in my opinion. Meanwhile, Scary Face makes perfect sense.
Leer, however, would fit in perfectly.
Also, to those complaining about "poor" coverage: Its two STAB moves are unresisted, meaning you hit all walls for neutral. You actually hit Super Effective on Blissey, Cresselia, Regice, and Celebi. This thing can never have poor coverage, ever. Stop complaining about having one of the best attacking types in the game.
Exactly why whether or not it gets punches is completely moot, as well as Power Whip. Thus my lack of major opinion.
Looking at the level up list, I really feel like removing Endure, Shadow Ball, Hypnosis, and Nightmare. This would make it learn its last move in the 60's (yay) and only remove its contested ability to sleep its enemies competitively.
I'm fine with removing those moves, as long as he can still learn the Shadow Ball TM. I think it'd be interesting if a Nasty Plot set was actually gimmickable.