the eye doesn't zoom... it has the convex on the lens changing, meaning the conceptual use is incorrect -
in the real world, if that is your example above, there is no changing of the FoV... how the eye sees, is completely different to how camera sees.
I can accept you've given some thought to the 'problem' some suffer with spotting a target and your idea of locking the FoV and altering the DoF could have some merit... at least it would be good for screen shots.
Lighting, as you mentioned, and others have mentioned before, does factor in a bit - we'll have to wait and see what EDGE brings in there