Interesting idea. Have you thought of a blender knob? That way you get volume and, instead of a selector switch, you have a knob that , err, blends the pickups.
Yes I have, but I wanted to try to do it with what I have first. I was thinking I could have 3 knobs, where one is the blender, panning from one to the next, and the other two would be the volume controls.
Stereo jacks are usually used to turn off active electronics in guitars so I don't think you'll need one. I'll have a look around for a diagram for you see if I can find anything.
My dad and I were looking at the wiring, and we think that there is no way to do it except with some sort of switch or stereo jack. The problem is when you turn one volume pot all the way down, the guitar stops making sound. I think that they are both independent (you can hardly tell with SD's) but when I open the circuit (turn the pot all the way down), and since both are part of the same circuit, the sound is cut.
But if I get a stereo jack then I need a stereo cable (probably).
I'll bet someone will come along and make me look stupid and prove me wrong :P !