So the current app I'm working on features lots of hard drawn animation. Some of the objects are quite large, and can take up a significant part of the screen when animating. So while I was making the sprite frames for the main character it occurred to me that I have to waste a lot of texture space when creating the frames. This is because the sprite often changes proportion quite significantly, and I end up creating my frames to the bounding box of all the frames, not each frame individually. In this specific case, it leaves roughly 30% of the texture space unused.
So it seems to me that a nice improvement to animation system would be to allow each frame in an animation to have a different drawing rect as well as a different UV rect. Then you could simply animate your sprite in the scene itself, and have a photoshop script do a crop on each frame, place it into a sprite sheet, and record both bounding rects to a file for easy loading of animations. This would save a lot of memory in some cases, as you could pack the sprite sheet much tighter.