I know all about 3D-Coat, I own it, have worked with it a lot through the years, know the devs, started this thread, and think an SDF modeling room would perfectly complement sculpting in the voxel engine. I think a NURBS-oriented CAD room is further away from the core of 3D-Coat than SDF modeling, which is a rising modeling method, due to a number of advantages compared to polygons and NURBS. Also, SDF modeling is not the same as voxel modeling. SDF takes place in shader space, and only needs to be voxelized if you want to sculpt on the model.
Have a look at this thread for more SDF info and examples: