I think if you add more gravity manipulation options, things can get very interesting. I am thinking:

• increase/decrease gravity by certain amounts instead of just having it as an on/off switch
• interesting for coop: a terminal where one player can control gravity, but has to stay there, while the other player has to solve the parcour. the player at the console can watch the other player through a window or cameras and has to change gravity in certain ways so the other player can pass obstacles or solve tasks

• external forces like wind that can change your direction midflight, and you have to dodge or utilize them
• objects that get pushed around by those external forces and are affected by gravity