Chances are what you're looking for has already been accomplished. This forum doesn't generally deal with this kind of mod, but if you head over to
Darknest, I'm sure there are some modders who have something that fits your taste. Keep in mind though, most of the edits are NSFW, and private servers are not supported by the community.
But to directly answer your question, to get the model files, you use CASC Explorer. To convert them to a format Blender can work with, called m2i, you use M2Mod Redux. To get them in to Blender, you need the blender scripts that come with M2Mod. Those same scripts will allow you to export the model back to m2i, which M2Mod can then convert back into Blizzard's format (M2 > m2i > BLENDER > m2i > M2).
There are guides and such as well over on Darknest, and here presumably, if you want to get into model editing.