Individual Pickup Selection
With Tone Select Switch

Versatile Pickup Selection/Phasing with Tone Select Switch
All capacitors metal film.
All switches DPDT (on-off-on).
Sw1 - Neck Select, Sw2 - Middle Select, Sw3 - Bridge Select Sw4 - Tone Select
R1 - Volume
C1/R2 Tone One, * marks low terminal of audio pot
C1 = 0.01uf when R2 = 250k, C1 = 0.02uf when R2 = 500k
C2/R3 Tone Two, * marks low terminal of audio pot
C2 = 0.02uf when R3 = 250k, C2 = 0.047uf when R3 = 500k
You may substitute other capacitors for C1 & C2 to suit your own tastes.

You can mount the fourth switch (Tone Control Selector) either with the other three or up near the tone controls, kind of nestled between them and forward of them. Again, mount the switch so it makes sense, toggle up for upper tone knob and vice versa.