Re: Hand Work
Footwork is the base from which balance and centering is achieved. Bad footwork leads to bad balance and therefore an out of control center.
Now for handwork it kind of depends on what you mean by "handwork." I'd say that most techniques require your hands to move properly within your "center" in order to achieve the desired technique. Certainly hand work is vital for proper pins. If your "handwork" is not controlled and your hands wind up out of your center, then you'll end of using more "muscling" in a technique than is really needed.
Proper hand positioning and movement is very important in Tenchinage for instance.