Keyframe-able Layer Controls
I know it probably presents a whole host of problems, but it'd be nice if we could keyframe layer controls. It would also be nice if effects that reference layers could be keyframed so that you can link them to a layer control.
If you're using multiple layers with the same Set Matte setup, for example, it'd be great if we could change them all with one layer expression control. But since they can't be keyframed they can't have expressions either. This makes the Layer Control much less useful than it could otherwise be.
Jacob Resch commented
+1 wanted to use this as a solution to another problem
but have to now think of another way