I was impressed when I saw the still pictures here and the massive list of animations.... but after actually trying it the model is lacking. It should open its mouth in at least one of those animations! All it really does is shake and rotate on different axes.
Can you add an animation where its mouth opens and provide the alternate model by itself so it could be used as a projectile? It would be so much closer to the original Pain Elemental with those minor additions. A Cacodemon skin would be nice too