What I would love is true 3d controls for a sprite, which would do exactly what you're asking. Mode 7 is basically a sprite that can be rotated in all directions, and placed in all directions (x, y, and z). If we had this, not only could we do 'mode 7' type stuff, but we could have true parallax scrolling, where the closer an object is to the camera the faster it moves. This could create some awesome perspective effects.
I know there's parallax effects via layers, but with a lot of objects on screen at different distances, it doesn't work well. It would be much more elegant to move them in 3d space - which would also sort them correctly (z order) and accurately resize them according to distance as well.
Example: http://ps2.ign.com/dor/objects/714612/d ... 43437.html