A tremendous tool would be to be able to animate points on a curve over time.
So say you have a cut-out character doing a walk cycle, you could animate secondary motion on the fly by just dragging points on a curve over time.
This would also allow to animate mask on the fly on a character to simulate shading as seen on many anime style of animation etc.
You can use the morphing tool for this.
I can see how it might be quicker if you can directly move the points but it would only work well for pencil lines not strokes.
Morphing works well for both.