hi,
affecting gravity direction woul dbe my first attempt and I am pretty sure it woul dbe the right choice in many cases. BUT that would affect EVERYTHING in the scene. so some other places may have items start falling where they should stick to their local gravity.
look at actually removing all gravity, and have objects using a custom gravity, gravity is only a force like anything else, so you can have that implemented manually. that would give you a lot of freedom.
Bye,
Jean