Looks good, sounds good, but what if all of this is a bit much for you? If you aren't into wires, jacks, and switches, but you still want to sound cool, you can simply replace the trimpot with a micro sized pot and an LED. That gives you another control parameter, and you can fit the pot and the LED into the space that is ordinarily taken up by the battery.

I've modded a few Danelectro pedals that way, and it's easy. There's more than enough room in the battery slot for the pot, and for the LED which indicates tempo. Heck, you could probably throw a switch in there for true bypass.