I would agree with the others that the best way to approach this may not be with a CAD tool but a polygon modeler.

However, as there is a need to have this kind of work in nurbs/CAD format for CNC machining, there are ways to convert polys to nurbs.

You could look at:
http://integrityware.com (for 3dsMax)
http://www.resurf3d.com (for Rhino)

or these VERY expensive solutions such as:
http://www.rapidform.com
http://www.geomagic.com