complicated wiring scheme halp thyme!
so, he have an HSS (H p90 p90 actually) layout, where both p90s are tapable at overwound and standard wound. we have a 5 way blade (can be a 4pole if need be) and Volume tone tone, all with push pull pots.
The humbucker is a standard 5 conductor (4conductor + braid).
the p90s are both 4 conductor (return, tapped send, full send, braid)
Volume is a universal volume, tone1 is a universal standard tone pot, and tone 2 is a universal low cut a la Dans explanation. the push pull on the volume should tap (untap rather) both of the p90s so that when its pulled they go to overwound (opposite of standard). Tone 1 pull should tap the Bridge bucker to the inside coil, and tone 2s pull should activate a hipass filter on the volume.
 This part is kinda important i guess eh?
for the switch
position 1: Bridge (series)
position 2: Bridge inside coil and neck
position 3: Middle
position 4: Neck and Middle
position 5: Neck
one last request, id like to keep the return lines seperate from the grounds, a la balanced send.
Im working on it, but help would be nice
ok max i have been thinking about this for like two days and what you want as far as switch positions go is not possible with your switch (position 2 is the problem) but if you are willing to let position 2 be bridge inside coil and middle then it will work otherwise you will have to get one of those super switches with like 24 poles.
The wiring dia gram you need is this:
as far as your taps and such the volume pot for the p-90s should be wired like this:
and your tone 1 pot for the bridge tap should be like this:
and i cant help you with the high pass filter be cause i dont really know how that works