...I tried it, and it is very difficult to play.
I also talked to Dieter Doepfer (his office is just 15 minutes from here) and asked him about modifications - as he was busy preparing for NAMM we didn't get thaaat far - but: mods should be possible...
Yesterday I took the theremin modules out of the Doepfer-box and into a separate housing...about 50 cm apart - and there were easier to play; next thing I'll try - time permitting - is a modification of the antennae, and I think that could do a lot also.
One thing to keep in mind is (regarding Eri's video) that the Doepfer-system is a modular synthesizer - so it is, what you make out of it; eg. I used the theremin-modules to control an A-110 standard VCO (not so nice) and then an A-111 high end VCO (three times the price ;o) and the result was much better the second time.
I also used the audio out and fed it into my computer, and voila: with a little filtering even the A-110 sounded great.
And one last thing: the Doepfer-theremin modules provide multiple VC-outs.