But that isn't safe!
If the player gets a bit of luck with his crosshair placement, no matter at what height you jump to try and dodge him,, he will hit you.
If he is fast enough to react by hitting you in the gap, he will hit you.
And if he is that fast, he is also probably fast enough to adjust his aim if he sees you jump too high or too low, and he will hit you.
I'm not saying it will happen EVERY time, but there is always a chance that you could die within 5 seconds of the round starting. Even when there's a smoke, sometimes people get lucky with their timing.
If there was some magical solution like you were suggesting without using utility, the people that play this game for a living would've thought of it, and we wouldn't even be having this conversation.