Another big issue here is that Series basses have a chambered body. When the body wings are being assembled the center core section is mostly cut away (there must be pictures of this in the Factory-to-Customer section somewhere). Since the top laminates are full thickness this isn't like an acoustic instrument at all, but it does mean that all the electronics are installed without much routing or channels being cut for wiring. Modern Series basses have the pickup selector switch near the other controls, but old ones have it out on the lower cutaway which would be a serious retrofit challenge if the body were solid (on a guitar like a Les Paul, they route the channel for the pickup selector in the body before gluing on the top).
The costs for having this sort of a mod done in the factory would likely be pretty terrifying, as just the electronics set is over $2000, then you'd have to add extensive routing and refinishing on top of that.
One less fiercesome alternative would perhaps see if you could get single coil Series-type pickups cast in the existing pickup shape you have and see if there's room to mount an unpotted hum canceller in the control cavity or another route. You would pick up some of the Series tone with the pickup change but you wouldn't have the Q-filter tone controls, stereo out, external power, etc.
David Fung
