For those of you craving a Theremin-to-MIDI controller, here's a free program you can run in Pd to do just that! Percussionist and music/technology blogger Charles Martin created this app in order to use his theremin as a controller for effects. It makes use of the "fiddler" object in Pd for pitch to MIDI conversion.
One thing that stands out immediately to me is the 0-127 (7 bit) control accuracy. Other Theremin to MIDI devices (e.g. the Moog Ethervox) output a 14-bit high resolution signal. Of course, it can be challenging to find a MIDI device that will actually support 14-bit signals for controls like pitch bend. In my experience, however, it's practically necessary when using a theremin as a pitch controller. With 7 bit resolution, you'd hear "chops" between the jumps in the pitch signal depending on how far you're bending it.
I've never used Pd myself, and I'm curious to hear how likely you would be to use a tool like this in a performance? Obviously you'd have to have a laptop connected to your theremin rig somehow - is that too much to deal with in a typical performance?