Re: Does this master series-parallel wiring diagram seem valid?
Your diagram does place the two pickups in series in any position of the 3-way. That second volume pot running parallel to the pickups is going to be parasitic, and some (higher) frequencies are going to find their way to ground, even on "10". In series mode, that could get pretty dark. Since you're dealing with a semi-hollow, I recommend making a cardboard template that will hold the circuit together while you solder it up, but then also use it to keep everything together to test it all before beginning the process of fishing all that back through an F-Hole.
As far as the S-1 is concerned, no one said the knobs have to be mismatched... you're allowed to change the other 3
As for no-loads as volume, I'll concede that with enough DIY modification you can make a lot of things happen. That's a fairly advanced operation, though.
I'll add a couple other options...
1) There's another way to wire the push/pull that eliminates the issue with the volume knobs, however, the series mode not override the 3-way. In other words, series mode would work in the middle and neck positions, but the bridge position of the 3-way would effectively be a killswitch in series mode. That may or may not be desirable.
2) If you want to keep two control pots and like to experiment, there's always the G&L PTB tone circuit. I've used this circuit on a couple of my guitars with complex coil switching so that I don't have to remember which coil combinations use which tone pot. The bass control might also help with taming that fat series mode.
I know I'm complicating it further by throwing more options at you. If you decide to wire it up as you have it drawn, please report back because I'd be very interested in hearing your experience with how the volume pots act in series mode.
