My experience with a pedal very similar to this is that it really benefits from compression on the clean side. The distorted side has no dynamics whatsoever, and that's why it seems to ride on top of the clean tone. I put an effects loop going into each side, but we've ended up just sticking the comp in front of the pedal itself. Subtly different effect from in the loop, but it works better for our situation.
Then it can take some fiddling. I had to do some silly things to balance the gain, voice the distortion, voice the LPF on the clean side, and get the blend pot to offer a useable sweep.
I agree that it would be more flexible with more knobs, but there are a lot of good tones in mine, from a subtle "bass expansion" type thing that adds just enough first octave to help the bass translate on small, bass-deficient systems, to a pretty nasty buzz saw thing. I had Les Claypool's bi-amped system in mind when I built it, and there's definitely a little bit of Pork Soda in those two knobs.
I guess I'm not trying to hijack this thread, just trying to defend the basic premise. It can work. I don't have a schematic to show you. It's three buffers (one with a little gain), a wide open Rat, and a whole bunch of half-assed, dimly remembered hacks dreamed up in simulation and then "perfected" on the breadboard. If I had it to do again I might try to put a compressor inside the thing, but I highly recommend the loops. Put a wah on the distorted side, or a phaser, maybe a delay...
Edit - rather than double post, since there have been no replies.
Reading that other thread re: adding dynamics I had the idea that we could maybe do the opposite of what I suggested above and add some expansion to the distorted side so that it follows the clean a little better. But then, if you just used a more "transparent" circuit for the distortion...
Honestly, though, if you're actually looking for ultimate flexibility you'd be better off just building a Buff N Blend or other splitter/mixer/looper thing. That's really all this thing is.