After doing a bit of research, our local builder is not working in a vacuum, at all....
I had thought the aftermarket guitar parts industry supplied those who want to repair or upgrade their instrument, but it turns out assembling custom guitars from these excellent replacement necks/bodies/electronics/accessories and hardware is quite a popular hobby - or a way to build that unique instrument with your individual tastes in mind.
One gentleman maintains a website chronicalling his experiences, and offering advice and information -
http://www.customstratocaster.com/