I'd like Premiere to have something like Corel VisualStudio's Pan & Zoom manipulator. It opens a new panel with two views of the current clip. The left-side image has a square overlay that lets you zoom in or out of the image just by resizing the overlay. On the right, you get a view of what the zoom will look like on the "full screen."

This way you can zoom without losing sight of the image as a whole, and it is much, much easier to resize and re-position your keyframed views.