These are all very interesting ideas. What do you think about representing the gravity changing objects as magnets? The player would have to orient them properly using some switches on the floor, ceiling, etc in order to prevent them from attracting its body for good. It's just an idea for some of the levels; we need many different ideas in order to take our game to its 100th level without boring the players. Check out World of Goo to see how a simple, repetitive game concept was turned into a great game.