If you are into capacitor variance to influence subtle tone changes, this might interest you. The UTA Vari-Cap cable is equipped with a capacitance change knob so you can hear tonal differences, hear it here:
Vari-Cap- QUICK OVERVIEW from Undertone Audio on Vimeo.
My concern here is that switching device itself, it gets in the way if you wish to loop it into the strap gap at the body end & it's not proximate enough for an easy reach. It's also costly- almost USD100.