"pos #2 & #3, both pups "see" both volume pots": I want the volume controls to always control their independent pups. Obviously, only when engaged/selected. So yes, in positions 2 and 3, neck volume still controls neck pup, and bridge volume controls bridge volume. This way, I can control their independent volumes to balance them as needed.
The problem is, this isn't physically possible. You're asking the rotary switch to act as a mixer, which it isn't. It's just dry contacts. When neck and bridge are "on", everything is shorted together. The "neck" electrons don't actually know where they're supposed to go. That's why we have expensive mixers.
There is, however, a workaround that Les Paul players have used for years. It isn't ideal, but works. (Somewhat.)
You just reverse the in/out of the volume pots. This has two affects:
1. As you turn down the volume, you increase the "load" on the pickup, thus slightly changing its character. In other words, with the bridge turned halfway down, it will be a 250k pot.
2. When both pots are on "10", both pups
still the combined 167k load.
You can do this by just doing the mod I show in the attached diagram.
There is another, more expensive, solution. Bartolini, and others, make an in-guitar mixer/preamp precisely for this purpose. It isolates, and lets you adjust gain on the two pups independently. But it's about $100 and requires a battery be installed.
