I would love to help, as I would love to know more about this particular area. Sadly, I know next to nothing about the NIF format. I heard someone say there was a way to remove the extra data that handles slanting feet and lower legs on inclines, and assign the foot portion of the NIF high inertia, friction, and gravity, to keep a humanoid stationary on a moving platform (moved by collisions), however I have absolutely no idea how to begin to become educated on how that could be done either.
Best of luck to you though. I feel your pain; sometimes my awesome modding endeavors feel like dancing with two left feet! XD
At least I know scripting pretty well. =P