Hi Rick,
Pickup construction here more or less follows standard protocol as what anyone else does when doing conventional winding. I see you found your way to the pickup winder's forum; that's a good souce for a lot of useful information although I find many posters there a little too ascerbic for my liking so I don't participate there.
The split single shown is incorporated in my lap steels. I've also wound a bunch of standard single coils in 4, 5, 6, 7, and 8 pole configurations depending on the instrument they are being produced for. The split coil bucker is just a variation of the single coil designs, though.
The coils shown are pattern routed from 1/16" and 1/4" Garolite and joined with the 1/8" Garolite baseplates. It's a simple matter of gang drilling the top and bottom coil plates and pressing in magnets with a temporary wood spacer to hold them at the proper distance apart. It's difficult to explain in a few sentances the entire pickup making procedure. I used 95 photos and accompanying text to describe the pickup construction process in my lap steel construction guide, so you can see there's more to it than meets the eye.
I don't know about the finish on the 3D printed bobbins, but you need them to be both uniform and EXTREMELY SMOOTH to successfully wind. That might prove to be the proverbial fly in the ointment for you.
As far as time goes, if I did only a single pickup it would take about an hour start to finish. The bobbins are only a few minutes of that time if you have the bobbin patterns already done. Obviously the time per pickup goes down if you batch wind several.
I only wind because I'm interested in a particular configuration that's not commercially available at a reasonable price, or special pole numbers or pole spacing considerations. From an economics perspective pickups are available as imports at a price that does not justify your time or materials costs if you can use an off-the-shelf configuration.