Brian, 3D scanners and printers are really fantastic bits of kit, but they have serious limitations.
The scanning usually gives you a surface to work with, then you have to use a 3D CAD package to manipulate it.
The printers are used for prototyping and the material is often contoured quite badly and needs a fair bit of post-processing. And its plastic, so ideal if you are using it for a casting, but the OP has already ruled that out.
Its quite funny that the scanning and printing are often put in the catagory of 'Reverse Engineering', which we all know is a polite way of saying.... copying. When the Chinese do it they are bad, when we do it, we are 'reverse engineering'.
Both great tools, but not really suitable in this case.
If the OP really does have a good engineer working on this project then I imagine all they would need is a vernier / micrometer, pen, paper and a fairly decent machine shop capable of doing very intricate machining operations.
This is the sort of thing a model builder would be great at.
And by 'model builder' I don't mean someone who does airfix kits, I mean someone who can create very small scale detail replicas. I know one such person and they are not cheap to get work done by.