I have suggested before of making a variety of reusable appear/disappear animations and then linking that series back to the base animation. You could easily (given your animation skills) create ALL the appear/disappear animations you find in games like Diablo III or Torchlight II, and tune them directly to animated placeables, or even animated tiles.
I'm pretty sure you've personally been around long enough to know the basics of superanimation, but for those people not yet familiar, this is how you would do it:
All you would have to do is create an animation including JUST the appear/disappear animations and set:
setsupermodel <this new model> <animation normally called on by your creature>
So then, if you want to make it reusable for all creatures with that base animation set, for each creature you want to behave that way, just clone that creature and set:
setsupermodel <this creature> <your new appear/disappear model>
I've begun work on just that, but only for basic skeletons. I'm currently working in a different scale (and node tree) than the normal models use, so you won't find my work useful in the slightest until the series is completely finished, otherwise I'd just pass you what I already have. Granted that the NWN base skeleton is just a clone of the human, it should also make interesting vampires that can rise out of coffins, or with another appear/disappear set, make orcs that scale up out of a hole like in Moria.
My initial intent with my own work is to completely clone all those animations found in TL2 first, then capture anything I may want from D3. All those animations make the game what it is, and I want that for NWN.