Hi Ben,
Electric guitars use magnets and coils to make sound. (Electric Guitar Pickups - HowStuffWorks) . To build one you need a 'pickup winder'. As shown in this video 1966 Telecaster pickup torn down and rewound | stewmac.com
These things can be expensive: Schatten Pro Pickup Winder | stewmac.com
One big drawback is that you have to hold the wire while winding. Can you build a 'no-hands' pickup winder? One that holds the wire and moves in the right way to wind a pickup?
Also in general people talk about the number of 'winds' a pickup has in addition to it's resistance when trying to tell you how it sounds. The problem is winds might not equal resistance in all instances. Most pickup winders just count winds but it would be AWESOME to set a resistance like .. 11.5K of 7.5K and have it wind until it hits that resistance.
Thanks!
Collin