Well, player movement and the like sounds good. I think we could still need some people doing that.

-George, looking at your prototype I believe we should have two sorts of movable elements in the game: a) pushable/movable elements that stay fixed to side they start off at. b)pushable/movable elements that will adjust to the new gravity when it switches. The number of puzzles will be greatly improved. A simple pseudo-physics simulation should do here, I don't think a full physics simulation would do us good in this case because it won't work properly with the different gravity-modes.

-We need a very cool animation (in my oppinion) for the main characters when switching from one gravtiy mode to the other, like him turning around quickly (doing a somersault) in mid-air.

-The time-traveling might need a few more twists to it. Example: you need to reaload your time-traveling-ability by collecting watches (or whatever. think: prince of persia's time-sand) before you can reuse the ability. Otherwise it's just a "i'm gonna keep switching time cause it don't cost none" until I found the exit here".
Would also like nice scenery there: a broken bridge (I think that was superku's example?) that wasn't broken in the past, but when it wasn't broken, it was guarded by two very large and very bad guards etc.

-Time Traveling could get a nice effect, I think. Like some sort of motion blur, very short, but visible.

There. My two cents.