No offense, but why design one when there are several thousand to choose from already? MOD one, yes, that I understand. Every pedal can require a little bit of fine tuning to do exactly what you want. But designing one from scratch is a rather pointless task. Even if a person comes up with a new "design" it ends up sounding and behaving exactly the same as one or more of the thousands already i existence.
I agree. I'm working on an EE degree right now, and I'm at the point in my studying that I feel compelled to start designing stuff. The problem is that everything has already been done in the world of stompboxes. I end up looking at circuits I like then adding things to them. One of the first pedals I built was the Blue Clipper on the Tonepad site. I love the sound of that and have added a tonestack, added clipping diodes in the feedback circuit, and played with values until it become something pretty far from the original. It's now probably just like something else, but who cares.