interesting question. :-)
Right now, we already do stuff like that to a certain extent with several "second" solo instruments in MIRx (Mode), mostly woodwinds and brass. Here we try to outwit physics by using different Characters (aka. PreEQ), VI's Humanisation features and of course different positions on a stage. Still you will run into phasing issues from time to time. This would happen more often when you try to build an actual ensemble from a single instrument. - The only technique that is able to make this work is VSL's "Dimension" approach, but that's not what you're asking for.
Personally I would try to use the actual ensemble sets of an instrument for unisono work and switch to solo instruments for individual voices / Divisi. In case you're just missing certain articulations for unisono ensemble lines, the "Appassionata + Solo String"-trick might be worth a try: You take the ensemble samples for "size" and "flavour", while you add all the missing agility and articulations by mixing in an additional solo instrument with much more detailed articulation work.
Other than that, we have no plans to invent an "artificial ensemble" feature right now, but thanks for sharing the idea!