I had once thought of developing a design pipeline much as you have
described of sculpting in clay, scanning, cleanup, scaling, and
prototyping. I had already started using Rhino3d for the prototyping
part, but wanted a way to do design in a more organic and sculptural
way than engineering software offered.
As I started to research scanning systems and the software and
processes necessary to alter and repair the scans I soon realized
that this would be an expensive and difficult way of developing
jewelry models. What I have opted for is to learn Zbrush by
Pixologic. Cheaper than a scanner, compatible with Rhino3d, and it is
like sculpting virtual clay. I don’t have to worry about fixing scans
and stitching things up, etc. Plus I have the power of a computer to
aid in the sculpting process.
Basically, I felt that the effort to scan something and fix
everything to get it ready for prototyping would be just as technical
and difficult as if I were to just learn to sculpt it on a computer
in the first place. I imagine that you could use a scanning service
to do the scans and cleanup for you. You would then need to use a CAD
program to scale, mirror or whatever you needed to do to prepare for
sending it out for prototyping. Perhaps it can all be outsourced.
So yes, you can develop a design process as you describe, but you
will still need to learn more about pixels, quads and whatnot than
you may want to know.