Paul, that's a similar idea I had for my Fender. I wouldn't mind using four controls on the control plate and shifting the plug to the side, maybe even inside the strap pin (wasn't that even on the West meets East Featured Custom?).
On the other hand you could get away with even three controls if all of them were stacked knobs:
vol/pan, bass/treble and filter/Q (possibly push/pull)
Can't you even get the plug as a combi-plug the way as they come on some mixer inputs, where you'd have a female speakon w/XLR and standard jack input in one? This way you could probably get phantom power and balanced output if needed or just the standard phone jack.
I just believe the stacked controls can become uncomfortable so I probably would stay with a solution where I'd had as few stacked controls as possible, who knows.
This is still a long term project for me as right now all my money goes into an epoxy job of my fretless Fender neck. Later I will address the pickups and electronics...