Thanks so much for your post! I would love to have modeling support. For the next release I am actually planning on adding a bunch of models and working on trying to make adding them to the maps as easy as possible.
As far as how to add models, they need to be md2 or md3. I don't know a lot about modeling and about adding the models to cube 2 but I certainly want to learn and to find the easiest ways possible. I don't know if this answers what you are looking for but it seems like a good start:
http://sauerbraten.org/docs/static_wiki/MD3%20Guide.htmlTake care and thanks for your interest!
-mike