I just meant sensor pixels, because you’re obviously losing those when cropping, but you get the same perspective as from larger focal length (since you’re not moving).
I agree that the images correspond to the same region in object space. Further assumptions on optical resolution don't work well, as the optical resolution depends on the f-number.
The angular resolution depends purely on the aperture diameter, not the f-number. There should be no difference between capturing the image in high resolution, and blowing it up for a lower resolution sensor.
All that should be needed is a 200mpx sensor that can output the entire frame in 12mpx, and 12mpx of the central area in full resolution. It's similar to how our eyes work.
this is an assumption that goes against the concept of "f-number" so if one does it, they should not expect to get to anything sensible.