Hi Geoff
The book is easy, that is Morane-Saulnier, ses Avions, ses projets, by Henri Lacaze published by Lela Presse
As far as I can judge (my French is basically non-existant) it does not state specifically it was designed as a two-seater, only that the outcome was that.
As mentioned before it was based upon the aircraft (c/n 29) built for the Russian military attaché in Paris, Rebikoff (but read ordered by the Russian Government). That aircraft was a three-seater.
If the Russian's follow up order for the, by then named type, (VR/WR) stipulated two seats is not stated, but I feel it is pretty likely.
As for the inserted nose section, yes I have also thought about that, and I also go along your thinking. The normal Morane two-seater was a pretty close-seating machine, while with the VR/WR we have a much more spread out crew (pilot in the rear) and a very clear tandem seating. So, yes, very much a question of balance.
Cheers
Stig