This is a small module. It uses 3 variables and 2 rules to allow you to enable flight near identical to that seen in sigma/mercy ultimates.
Simply set the "Flight" player variable to true or false to enable and disable.
Also lets you set the "FlightSpeedMetersPerSecond" player variable to alter the flight speed. If you don't alter it, it will be 5.5 meters per second by default, which is Overwatch's default movement speed.
When turning off flight, movement speed will be set back to 100%. So, either edit only the end of the flight rule to reset it how you'd like, or just remember to do this whenever 100% is not the desired speed to return to.
Player.Flight = False;
Wait(0.016, ignore condition);
Set movement speed(Player, desired speed);
Note: There are a few movement abilities that rely on a player's movespeed that will not work while flight is enabled, such as most of Doomfist's abilities. If this is important for your mode, you can create some workarounds where flight disables temporarily if they use one of such abilities.
Here's a quick demo:
