I've drawn up a couple of diagrams… but, the tricky thing is it depends on how your pickups are wired (internally). Some manufacturers match colours to pickup poles, others match them to inner/outer coils. For example, with some pickups the black 'hot' represents the 'start' of the inner coil for both bridge and neck, but they have opposing poles so they can be linked in a hum cancelling pair. With other manufacturers the black may always be the north 'start' and the green always the south 'start', so you have to match opposing colours when you are linking split bridge and neck coils. As such, without knowing your particular pickup's configuration I've drawn the diagrams like so:

Blue: inner start (hot)
Yellow: inner end (series link)
Red: outer end (series link)
Green: outer start (ground)

Therefore, you'll need to work out which pairs of wires on your pickups are for the inner and outer coils etc. so that you can link them in inner/outer hum-cancelling pairs. Make sense?

Diagram 1:
Push/Pull pairs for volume and tone for each pickup, allowing individual series/parallel/outer coil/inner coil switching. Plus, a separate switch giving In Phase/Out of Phase between the pickups and a kill (mute) position.
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BV = Bridge Volume, BT = Bridge Tone, NV = Neck Volume, NT = Neck Tone, up = Push/Pull up, down = Push/Pull down

BV down, BT down: Bridge series humbucker (standard)
BV up, BT down: Bridge outer coil
BV down, BT up: Bridge inner coil
BV up, BT up: Bridge parallel humbucker

NV down, NT down: Neck series humbucker (standard)
NV up, NT down: Neck outer coil
NV down, NT up: Neck inner coil
NV up, NT up: Neck parallel humbucker

The phase switch changes the phase of the bridge pickup only, so you'll only notice it when combined with the neck pickup in the pickup selector middle position. In the 'kill' position on the phase switch it just shorts the jack's hot to ground to mute the guitar. They're a little pricey, but a double-neck style On/On/On 4-pole toggle switch would work nicely for the phase/kill and should fit perfectly in that larger 5th hole (rather than trying to fit a mini-switch). But, the phase switch is just an idea, you could do cap switching or a rotary switch or whatever.


Diagram 2:
Similar to above, but only one pair of push/pulls (neck volume and tone) that switch between series/parallel/outer coil/inner coil for both pickups together. Standard pots for the bridge volume and tone. The 3-way toggle switch still controls which pickup(s) are selected, but the push/pull settings control how both pickups are configured. Again, there's a separate switch giving In Phase/Out of Phase between the pickups and a kill (mute) position.
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NV = Neck Volume, NT = Neck Tone, up = Push/Pull up, down = Push/Pull down
(Push/Pull setting affects both pickups)

NV down, NT down: Series humbuckers (standard)
NV up, NT down: Outer coils
NV down, NT up: Inner coils
NV up, NT up: Parallel humbuckers

If you'd rather have a series/parallel setting between the pickups instead of a phase switch it's easy enough to do, but there are some caveats to how it can be used. Let me know if you're interested in that option.


Anyway, that should give you some ideas for using push/pulls for series/parallel/splitting.