This certainly isn't a new idea, but I've totally been bitten with the diy bug. My plan is a distortion unit that utilizes a 'pluggable' architecture. The idea is that you could plug in small modules at the various stages of the distortion so that you can change the sound. In any given distortion unit, you generally have 3 stages: Input, Feedback loop (where the distortion actually happens), and Output. The kind of modules that I am thinking about are filters (to color the sound) and specialized circuits on the feedback loop to change the shape. There is no reason why other circuits couldn't be added to this as well. Things like a ring modulator, resonant filter, or something.

Each plugin unit would have its own bypass switch and controls. Also, when a unit is not plugged in, it should just bypass the signal, rather then break the circuit. I'm not entirely sure what kind of plug I should be using for this part however. I do have the circuit block diagrammed, the next step is to block diagram the plugin elements, and then to do the physical layout. After that, I can think about the actual components of each piece.

As I keep going with this project, I'll post it.