At one point I was looking for a servercmd for movement. I couldn't see how it would work without it.
If you think about it clientcmdtimescale is completely client sided and can be used to slow your player from a knock back or gravity.
Even if you reduce it on the client side, it doesn't actually change how fast you're moving. You may appear to be moving slower, but your actual velocity is still unchanged. Thus if you do 0.2 timescale on the client side before you hit a wall/floor, you'll still die of impact damage, even though in your rate of time, you were moving incredibly slow.
Technically you should be able to float at any time (modifying the game through a 3rd party program though), seeing how lagged out players become frozen mid-air.