I know its not possible to emulate some things like the actual sound of it being driven/distorted on input, as its a very unique sound. Also the little imperfections and noise such as hearing the lfo
But some kind of dirty filer with the envelope follower which opens and closes the gate based on what goes in. It used to be great for drum loops or anything rhythmic.
Another thing the Sherman does which is cool is that filter 2 can be synced to filter 1, but lower down in musical values. Like an octave or 5th down.
Anything which went in also came out with a massive bottom end.. a weak bass from a vst synth would sound just huge!