Adding the ability to use alt and shift to control what sides gain or lose width/height would be pretty useful.
For example, if you want to increase the width of a face on a fuel tank, you would have to press the width arrows a few times, and a considerable amount for larger widths. While using alt, you can increase the width of the face with the arrow gizmos (the blue 3d ones) without increasing the x offset at all.
With shift, you can increase all sides (on a face) with only one arrow. (Note that I mean that you add width to each side individually)