I would like to see these planes as they were decent aircraft that were used in the early and middle years of the war. They were no late war monsters (like the LA7, P51D, or Fw190D) but were capable aircraft that have been rarely if ever modeled.
As for rare I am willing to bet that enough I-16 were produced to allow it not to be considered a rare aircraft.
I will admit these planes may not be all stars in the main arena, but for scenarios, or combat theatre we need more variety and the flexibilty to create more acurate matchups adding these planes would help both the Battle of France, and Russian Fronts.
I could even see adding the D520 in both German and French colors as it was used by the Germans in Large numbers after the fall of France in training and a few combat units. All reports show the plane to have been an even match for the Spitfire I, and Me109e models that flew in the same time period.
In any case its fun to talk about what we would like to see, and you both have some valid points on why these planes should not be modled.