The "issue" I've been finding trying to dial in my Ceritone Centura (A pretty exact Klon clone right down to the same enclosure) as well as my Chase Tone Secret Preamp (which is a recreation of the EP-3 Echoplex preamp circuit, minus the tape delay part) is that there is a non-linear relationship between how the pedals sound over a certain part of the neck, strumming a certain way, and how any drive block setting sound, as you change your playing dynamics or hit different notes.
I can get a FET Boost, or one of my favorites the MicroBoost, to sound pretty darn similar when I A/B strumming a certain chord, but then those same settings don't respond the same to something like light fingerpicking higher on the neck. I can then adjust the drive, EQ etc to closely emulate that setting and tone, but then hitting open chords with a pick won't sound the same.
This is the same issue I run into with fuzz pedals. I can very closely nail the tone of a pedal with a certain knob setting, and volume pot setting on my guitar, but then when I change the volume pot, the tone of the pedal and the tone of the drive block emulation stop being so close.
Don't get me wrong, they both sound good, but I just don't think its possible with the existing drive block behavior to really emulate a pedal in the same way we have the amps modeled. With the amp models, the model changes very similar to how the real amp changes with adjustments to MV, drive, tone stack etc. Its a true model of the circuit and its non-linear behavior.
I don't think the drive blocks are able to do that this point in time.
The Chase Tone SP for example has a non-linear frequency specific phase shift as part of its circuit. This is one of the things that accounts for the tonal coloration of the EP3 and why so many guys used to run though them as a tonal tool, not as a delay. Some still do like Eric Johnson.
Point being though, that if the pedal your trying to match isn't just a certain level of boost, with a mid hump at a given frequency, but is instead introducing some phase shifts at certain frequencies depending on amplitude etc, your not going to be able to just tweak the mid freq and mid gain knobs in the drive block and emulate it.
You'll get close, and have a very cool and usable tone for sure, but until we start to have true circuit level modeling of specific pedals I think the drive block is going to always be just a good approximation at best.
One of the things I hope we may see in the coming years with the III is actually having some modeling changes for the effects section to where a given drive pedal will behave like-for-like in terms of knob settings, dynamics etc with a hardware pedal.
Right now I can take a Fender DRRI and set it a certain way, pick up a given guitar and if I dial in the model the same, its going to sound 99% identical. The amp modeling is that good.
What I can't do right now is set my Skreddy Mayo triangle style big muff to a some given knob settings, set the drive block controls to those same positions and have it sound the same. That isn't the end of the world, and the muff style fuzz tones in the Axe are very good, but its just not like-for-like.
Maybe it never will be, and again, that is fine, but it would be kind of cool if that really was the case.
We've had artist send their unique amps in for modeling, so it would be kind of cool to have an artist send in a specific copy of a famous drive pedal they use in their rig, and then have a virtual emulation of that exact pedal with its own unique component variances etc all modeled.