@Zugothsss - It is technically possible to export WOW models to NWN and keep existing WOW animations. Here's a video of one of the proof of concepts that I did, showing just that. However, the chief complication is how the animation keys come into Max when imported from the WOW model. For lack of better terminology, there are "regular" key frames and "baked" animations. All NWN models (except the horses, AFAIK) are/were hand-animated and so have very few keyframes per second of animation. This is where an animator took two spots on a timeline and animated between them. For instance, in keyframe zero the shoulder might be rotated so that the hand is at the model's side and at keyframe 30 (one second later) they have another keyframe (at frame 30) which rotates the shoulder joint by 90 degrees. There are only two keyframes in this example, just to be clear. NWN interpolates the position based on the start and end for every frame inbetween. This is called "tweening", BTW. Very low memory consumption with that method. However, some games bake their animations which mean instead of two keyframes, one at the start and one at the end of a range of motion, there would be 30 keyframes in our hypothetical example, one for each frame and each defining exactly how much the shoulder would be rotated in that frame. This eats up a lot of memory. Memory usage for animations is not the hugest deal in the world but if you had a lot of creatures each using unique, baked, anims for their full range of anims, there might be a performance impact. I believe that imported WOW models come into Max with thier keyframes baked. I could be wrong, but that's my recollection. If that's the case, in many ways it's easier and more tempting to just use existing animations for something similar that already exists in the game. After all, for the most part, animations are just rotations along either an X, Y or Z axis and only something like the root dummy would have position animations.
@NWN_baba yaga - Spot on about the nightmare of scaling with bones and skin mesh. I can't give a more thorough description of the solution at this time, but I was able to work around the issue the following way. Performing these modifications on models which do not have animations is very important. Just supermodel them into the model you wanted the animations from. I also want to include the tidbit that, while it probably won't come into play because NWN doesn't generally use Max bones for bones, there are interesting tools to help with the scaling of Max bone object in the "Bone Tools" tool in Max. Very, very handy and very obscure but, IIRC, it allows true scale resets on bones in ways that NWMax can't cut with its methods. Again, though, I do not think that bit will really come into play for you or me or anyone else except in rare situations but I wanted to provide it for completeness.