That kind of a thing will be coming eventually - T-Splines (http://tsplines.com/) is one of the starting things like that.

The only thing is that SDS modeling has kind of an overall different toolset, it's kind of more focused on moving 3D points around and sort of works more like sculpting.

NURBS modeling in MoI is set up mostly around a different type of method, more like drawing curves and constructing things from those curves. It's kind of more like drawing or illustration than sculpting.

For shapes with little lumps and bumps and small details like a face, the SDS sculpting method works great. But the drawing/illustration style method tends to be better and faster for industrial or mechanical type models.

- Michael