Hi Andras - with MoI v2 you can use the SAT format to move both solid and curve data back and forth between AutoCAD and MoI.

Unfortunately DWG is not a publicly documented format, so it can be more difficult for me to work with that format. In the future at some point I may be able to do something for it but I'm not sure exactly when that might happen.

But SAT format should work for you right now with the current MoI v2 beta.

The only thing that may be an issue is all your objects will come into AutoCAD as spline curve or "BODY" entities, rather than special purpose entities such as a LINE or CIRCLE entity. Things like snaps, etc... still should work fine on them though. But if that is an issue for you, you might want to check out Sycode's 3DM import plugin for AutoCAD, it could possibly help:
http://www.sycode.com/products/3dm_import_ac/index.htm

- Michael