There's nothing wrong with your original plan with the switch and by all means persue that. If it were me, and it's not, I'd want to utilize the buffer since it's all ready there and sucking pixie juice. I would at least try rolling back the boost and seeing how it sounds before drilling the switch hole. I think a 1M resistor between the output and ground would be beneficial to the circuit. Hopefully someone will chime in and confirm or dispell that notion. The idea that the buffered signal is darker doesn't really add up unless the output impedance is so low that it's lower than the next device. Robert makes 1 for 1 clones of these circuits, shortcomings included. Using a quick online calculator, it looks like theQ1 buffer stage output impedance could be in the 2k2ohm range. With volume and and boost maxed, that would translate to a very low circuit output. That's potentially fine if you're adding a 1M volume pot after. Idk. Maybe I'm backwards. We'll see if someone else chimes in.