We can add this in the next dot release maybe but what you could do right now is use Frame Numbers mode instead, setting two keyframes, one at first frame with value 0 (or 1) and one at frame 149 (or 150) for example that says 5000 for frame numbers.
This will then play 29.97 FPS for 5 seconds. I imagine you want to see the 1000 FPS in real-time to see the action not in slow-mo. You won’t be able to use the motion blur compensation (not designed for 33X speed ups).
And of course there is no way to have a computer display 1000 different frames in a second.
Pierre