I'm not sure if a VCS3 would be legally possible, with Robin Wood and Ludwig Rehberg still making them.
If it is, I'd love to see how Arturia would develop the idea. Probably variable filter types. The ability to draw your own waveforms as with the 2600V would be wonderful. If an Arturia emulation had that as well as the usual three oscillators there'd be no doubt in my mind about buying it, although I already have Ludwig Rehberg's software version.
A sinewave on oscillator three would be a good addition as well.
But better still would be a double EMS. The basic EMS design is great, but a little frustrating because of the limitations. David Vorhaus and Tim Blake both had double synthis. Vorhaus' synthi was basically just two VCS3s with the matrix boards wired together, but Tim Blake's had some extra refinements.
Note to Arturia: if you ever want to consider modelling a double EMS synthi, I can provide more info, and ask the current owner of Tim Blake's double about its availability for modelling.