I'll join in the search.
I'm thinking of a small coil winder for my first wind turbine generator. I've got a fair number of small steppers and was thinking along the lines of a simple pulse generator (555) to drive the spinner, then a pulse dividing chain to step the wire guide.
However I realised that the "scanning" of the guide would be a little more complicated, as the turnaround is non-linear, nor rotational, for want of a better word.
An old sewing machine in the family had a sort of nephroid cam to do the business.
Perhaps a look-up table could be written to map the guide to the spinner ?
I shall be using 22 swg(0.71mm) wire and looking at a spin rate of less than 100 rpm.
Are your needs for the guitar pick up very different ? I guess you are looking at much finer wire, and a lot more turns.
It's like doing jigsaw puzzles in the dark.
Enjoy today's problems, for tomorrow's may be worse.