A bit late to this conversation but the only way to properly fix troll style units for it to work on any windows version or cd/steam is to use the elephant skeleton as a base and move the bones (while keeping the hierarchy) into a postion such that it has a humonoid appearance. Then you'd need to make new animations. The reason the trolls crash is because there are hardcoded parts for each unit type in the rtw engine and the moment a certain action triggers something that enforces these bones to exist in the model the game crashes. Bones like the 'elephant_back' or 'saddle' are not present in the human skeleton used for these trolls (human skeleton uses pelvis, abs and torso instead). I used to have similar problems until I opted to use the elephant skeleton as a base, now I have flying humanoids in my mod.
There's a good reason why fellbeast do not crash and trolls, sauron etc does. If you wish I can send you my own setup which is suitable for trolls, ents and sauron.
Here are some useful tools:
https://www.dropbox.com/s/xsrh9wd11v...tools.zip?dl=0
The 3ds bone skeleton script automatically exports a list of numbers and bone positions and the python script converts skeleton files to text so you can paste this info in it and the use this python script again to convert it back to a skeleton file.