Sorry for being so late responding here.
Also, forgive me if I echo something I may have overlooked here. I'm in a bit of a hurry responding between rehearsals.
So. My thoughts on this. I've noticed from listenning to recordings of older theremins like the 91 series, Ethervox, and even the RCAs, there seems to be a difference in tone when one executes a glis from one end of the field to the other.
How much of this effect is caused by the speaker, vs the electronics is something worth exploring.
I'm certain this could be emulated, but just how to go about such an emulation is a challenge. Do you do it via sampling? The technology certainly exists, and the cost of chips needed to emulate with sampling that transitions with a cross-fade method from one charactor to another on glis certainly would seem to be doable to me. The resolution of chip based sampling has improved over the last 20 years.
Or, do you go to the trouble of back-engineering existing artifacts, and reproducing their circuitry? Tubes certainly sound different than transistors, or chips.
I know that modern theremins, like the Etherwaves, and even the burns theremins do this to some extent, but still fall short of reproducing the original sound of the pioneering theremins.
I would personally enjoy having access to a theremin which provided faithfully emulated reproductions of the original instruments.
Allthough it would be fun to explore a theremin that emulated conventional instruments, the whole point of playing a theremin, is that it does not, in fact, sound like any conventional instrument. It has it's own place in the world of instruments.
I have made a modification to one of my B3s, which now sounds a bit more classic. However, I have also noticed that one can simply adjust the equalizer on an amp, or mixer, and get some really interesting tonal charactors this way.
Anyway, that's my view on the topic. :)