Hi oli. Yes you can add voltage control and its a very easy process if you just want basic voltage control. 
 getting it to be 1volt/octave will take a LOT of work. 
The easy way is to use a home made vactrol. This is just a light sensitive resistor attached to an led. I've been scheptical of this technique for a long time but it actually works quite well. 
I'm doing a residency in Montreal soon specifically to develop and document these kinds of upgrades to the NovaDrone.