you could use the switch for a whole bunch of reasons..

for playability, you could try using it as a tone bypass or volume bypass. for a volume bypass, you'd set yourself up at say 70% on the volume, and when you want to stand out in the mix a bit, flick the switch. when you are done, flick it back and you know you are back where you started. A bit like a clean boost, but at your fingertips and not your toes.

same sort of deal with a tone bypass, if you use the tone knob at all. It would be a way to get you to "bright" on demand, and then return to your happy place consistently.

If you are feeling adventurous, you could run an addressable led strip light along the neck and use the switch to select colours.. that is pretty "look at me" though and may not suit your vision.

of course you could also embed your favourite effect pedal circuit in the back of the guitar and use the switch to control it. saves carrying around the extra leads and hardware and cleans up the stage floor. Shouldn't be too hard to rout a cavity and fit it in. I cant see it adding any extra weight either.