There are lots of ways to switch from rhythm to lead and this specific twin pot version of the N&N addressed a specific need for a specific Southern bluesman. It's a no-brainer passive circuit, and like all passive circuits there's gonna be trade-offs ... the same can be said of too many active circuits, too.
If you, as the pedal builder, have the ability to tailor the trade-offs in yer favor, then there aren't any (trade-offs, that is). And now yer talkin' a really custom pedal that does what you want, for your sound/tone requirements.
Adding in a DPST mini switch allows the signal from the pickup switch to be diverted to the volume pot or directly out to the N&N. That's the ideal setup, IMO. You can either use, or not use the N&N with the flick of a switch, and have the best of all worlds.
