Well, no idea if it's possible but working out from what I know...
There is a tutorial to import assets from other games. So I can only assume you can import you 3D models if they're of a supported format (Granny2 for models, DDS for... Textures?)
See this tutorial:
http://larian.com/forums/ubbthreads.php?ubb=showflat&Number=619563#Post619563The difficult part would be animations. Importing objects is easy enough. But you'd also need to rig a skeleton and animations for it, and import that into the editor and configure it. No idea how, but that's my impression of the current state to your question.
This is all guessing from an equally clueless goofball.
