Get a 7-way:
1. Neck
2. Neck & Middle
3. Middle
4. Middle and Bridge
5. Bridge
6. Neck and Bridge
7. All three
Then add series/parallel switching. Don't forget to include variants such as neck and middle in series, with them in parallel with the bridge, and all combinations of series/parallel combinations.
If you get dual-coil pickups you can also do coil selection. Don't forget to add switching so the coils can be series or parallel or singled (one coil or the other, selectable). If you do split the coils, don't forget that you can send one coil through the tone circuit and the other bypassing the tone circuit, straight to the jack, selectable by an onboard switch. Might be useful to be able to send the north coil of a dual coil pickup straight out, and the south coil going through the tone control, or reverse the two.
OK it's 2:30 on Sunday afternoon and I'm bored. As a good Canadian, I apologize. [/Hijack over]