I'd love a spritesheet function. This would be some sort of option (maybe while loading the rom or something like that) that would load all of the game's sprites in a style similar to a sprite sheet. This would be helpful for working with things like the health bar in Kid Icarus, which switches to a different sprite with each hit, and also would be helpful for dealing with more difficult games.
Also, camera panning would be really nice. Only being able to rotate the camera is really limiting.