Thanks Kevin and Larian team!
I'll take a look at guide and try again with new scripts.
About skinning to existing rig:
Spent a lot of hours trying to make it work, seems like it works only when mesh has nearly the same size and topology as original one. Trying to bind existing skeleton to mesh with different size/topology (in my case creature was bending forward, so its arms and head had different position than rig points), or when moving rig points makes distortions in resulting animated mesh in engine (don't know if it's intended, haven't tried this workflow in other game engines).
