Google a program called Endorphin. I believe they have a learning edition for free. Not sure though.
It's basically procedurally generated Motion Capture software.
It uses no actors, studios, or any of that, you simply set up the scene, give the virtual actor direction, and it does the rest in a very natural manner. I've no idea if those animations can be ported to BC, but i'm fairly sure they port to max, and max can downscale to 3.1 format and output a nif-anim, right?
Anyway, worth a look.