This is what I understand on modding animation:
-Create the new animation to use, save as a .cas file
-Create new skeleton with Vercingetorix's tool, don't copy base skeleton's animations
-unpack the animation and you'd get a series of folders where you can drop your new animation be used for the new skeleton
-edit desc_skeleton.txt, make the list of the new skeleton and add in your new animation in the list

Is this correct?
So I don't need to repack the animation file?