Add a feature such as severely increased recoil while in the air, or at least a huge weapon swing as you jump/land. Recently I've encountered more people jumpshotting, where they just keep jumping while firing to make them harder to hit. I don't see what being able to do this adds to the game so can't see a reason to keep it. It's so easy to stay on target at range while jumping that soon you'll just end up with all players doing it constantly, and I'm assuming your intentions weren't to create a kangaroo hunting simulator.