Hey Celludriel,
it is definitely possible and you are right, skeletons and animations are the hardest.
We are working on a guide on how to create custom characters. Like the
Custom Items Guides we will provide a custom characters guide that explains about our conventions for bones etc. and give some example rig files. Give that a bit of time though - it's a difficult guide to write and the person most knowledgeable is currently taking a short holiday
We're also planning on providing our exporters for max/maya to the granny format in a later update so you can convert models to the in-engine format.
Sincerely,
Kevin