I think some one already made a mod like that. You could use my upwardsgrav mod to do the skydiving part but you would not hit the ground eventually. I think the coolest mod would be my skiing mod with no ground friction! Unfourtunatly it is not possible to mod friction yet.
Sony: you can use the falling down mod (thats not what its called but i dotn remember so..bleh) and set the time to end right before you hit the groudn or something.