You may have found one of many solutions to dimming an LED, but you still haven't solved how to get a signal from the volume or tone pot that can be used to "tell" the LED dimming circuit how bright the LED is supposed to be. A possible solution, in fact the only one I can think of right now, is to install another pot in tandem with the volume (or whatever pot you want the LED intensity to correlate to). The likely problem is the guitar body may not have the depth to accomodate the extra pot. Looks like everyone is enjoying solving this little problem! Keep at it!