You may actually be more productive creating things in your preferred polymodeling environment and then use one of the new crop of converter tools for converting the sub-d model into a NURBS model that can be read in by CAD programs.

T-splines for Rhino can do this, also I think T-splines is built into Autodesk Inventor Fusion now as well, and there is also a converter for Modo called sub-d NURBS: http://community.thefoundry.co.uk/store/Power_SubD-NURBS/

That route may be worth a try for you since you wouldn't have to learn a new difficult and advanced level modeling workflow.

- Michael