You can still get a long exposure by accumulating many 1/5,000 exposure shots together. Just like a regular long exposure, this will still cancel out random noise and improve SNR, and also still has the tradeoff of motion blur. This kind of accumulation is commonly done in photography-adjacent technologies like spectroscopy.
Regardless, I agree with your larger point that the proposed system would be entirely impractical!
Regardless, I agree with your larger point that the proposed system would be entirely impractical!