Just a random thought: if the hardware can get 300 fps at 4k, and is able to do some basic processing on them in real-time, even if it can't output all these frames, it could be very useful for stills.
The camera could shoot 300 frames and select the top 10 (that seem to be the sharpest ones), just like the "Best shots" options from silent pictures. Might be interesting to try for wildlife.
Regarding dynamic range: if the sensor can output say 600 fps at 1080p, to get a 1/50 exposure at 25fps (180-degree shutter), you could combine 12 frames. If it can output 800fps, and you are OK with a 360-degree shutter, you can combine 32 frames. Assuming it does proper 2x2 binning (without introducing noise), this would give:

Just a theoretical way to get up to 13.5 stops of DR in 1080p without motion artifacts (with frame averaging).
Of course, you are not going to get close to a Nikon D810 image resized to 1080p
