I would think it's possible, especially if the pickups have 4 leads, then absolutely. Just unhook the pickup wires from the existing 3 way and the push pull portion of the tone pot, and wire it back up with the 5 way to core specs. The only trick might be figuring out which leads go to which coils, I believe the core models might select different coils depending on the blade position (inner vs outer/screw vs slug kind of thing) but not sure. And if you would need any different resistors or capacitors. Should be able to leave the existing push pull for the tone pot, it just wouldn't switch anything
On my S2's, I'm strongly considering swapping my volume pot for a push pull and wiring the neck pickup to it, so each knob will split a pickup. Great mod, have done it to a couple SE's, lots of variety. But the 5-way is very handy too!
