My wiring plan was to turn the rhythm circuit switch to a series/parallel switch (as shown here viewtopic.php?p=1370877#p1370877), have the lead circuit knobs as volume controls for each pickup (I guess one of them can be bypassed if we're in series), and turn the rhythm circuit knobs to master top cut & bass cut.
I figure I can wire the tone controls straight to the pickup selector output lug. However, I can't figure out how to incorporate the separate volume controls with the series switch. I'm not sure it's possible. Any ideas?
Separate volume controls will need to be wired "across" the pickup they are meant to control, before any switching. This is just like on any LP or SG with 4 knobs. You can consult any LP wiring diagram (of the 4-pot variety).
Be aware, however, that having a "master" tone circuit with bass/treble cut will mean that, when both pickups are on, the volume controls will interact to a certain extent. This may or may not be of concern to you.