I'm not so sure about this. Imagine you had a large cloud of planar mirrors, each, specifically can be aimed at any given point --even points that overlap. Wh

I'm not so sure about this. Imagine you had a large cloud of planar mirrors, each, specifically can be aimed at any given point --even points that overlap. While I agree that you cannot focus a whole image to a smaller area than the diffraction limit allows for a continuous lens surface, if you omit diffraction, mirrors could certainly do it.