There's an easy way to get unbalanced coils: spin-a-split, which is wiring a tone control as a second volume control, but for one coil only. I use that on neck HB's to add treble & bite, and reduce mids. Very useful. FAR better than coil split.
It's simple to convert a single lead HB to a multi-lead, and it doesn't require 4-lead wire. There's a connection between the coils, of a wire from each coil. Peel back the tape and you can see that connection. Solder a shielded wire to that and and run it down to the control cavity. In the Duncan color code it's the red & white wires. Technically you need 3 leads not 4, as the red & white are paired up, and that's what this added wire is.
To make hybrid neck pickups, I combine a bridge & neck PAF coil, around 1K difference in resistance between them. I use a warm magnet (A2 or UOA5) for sonic texture and still get sharp a high end and thinned mids. Bridge hybrids take a bigger difference in resistance, but the extreme of the '59/Custom hybrid isn't needed (7K vs 4.2K) to hear the unbalanced coils. The 'humbucker effect' adds volume & midrange, and reduces high end and clarity, so as the difference between coils increases there's less humbucker effect, and the pickup gets brighter & thinner, closer to a single coil sound.
I don't see any point in pairing up coils of similar resistance (like two PAF neck coils) as we don't have any idea of the differences or similarities in their windings, and you're likely to get little if any audible change in the pickup.
