I had a similar idea, but instead of some AOE effect it is a projectile, acting like a damage less rocket (like from Quake or TF2).
Enemies knocked into the air by it have their stamina and movement abilities disabled until they hit the ground. You can also use it on yourself. So shooting it at their feet to knock them back, or at your feet to rocket jump away. Also you could use it to do crazy movement tech, like shooting it at the ground before you land at high speed to keep your momentum, go higher up a wall by shooting it at a wall while going up.
Passives would be +1 stamina and +air strafing (half joking with this one).
Main issue would be being WAY too skill based.