as stated in the above thread, the difficulty is with the goop which is an ULTRA hard potting epoxy of sometime-- NOT soft black goopy crap that alot of pedals use. its been suggested to use a heat-gun and a high power vent or a REALLY hot iron to turn it into a powder that can be brushed away. But the problem is that the goop sticks to the components and the board-- it is poured all over it. sometimes, the epoxy even gets on the switch (ive seen pictures of this, as well as individual units that i have opened up).
this presents a problem when its a good ol blue style 3pdt-- cuz they breakdown
(everybody here knows, or should know that). Durham used to use durable Carling DPDT switches and a buffer on all models except his fuzz (and might have gone back to them).
my advice, if you want a work-a-like: (1) use half of the op-amp as a buffer ( i recommend the klon-style buffer) (2) use a simple tone control like the one you have on the zen drive (with the values tweeked to your taste) and (3) use the other half of the op-amp for the boost. the 'compression' switch well, that is more difficult to say-- my feeling is that it just sounds like it switches between two different sets of diodes or none at all (totally 'clean').
that probably doesn't tell anyone anything they don't already know, but i've been tracking this box for a long time now and, in my opinion, its the best solution besides just buying one, or buying one and ruining it by reversing it.
and, by the way, it is a really great sounding boost (the best one i've ever used)- because the tone really just ads presence and the bass gets slightly 'tighter' and more 'solid'-- not flabby. Soooooo, i would imagine that you can easily get this sound by using the same target frequency roll-off you get by adjusting the resistor/cap network from the feedback loop to Vr (or to ground depending)--- that is, just like a tubescreamer does to keep it from getting the 'Muddy' sound that some people dont like.
as for the op-amp... who cares? i've used a bunch of different ones that sound just fine-- different, but just fine.
best of luck,