A squash manipulator

If you do animation, you probably already know what is a squash. And if you know other main animation softwares like 3DS Max, you know what could be the squash manipulator in Blender.
Squash and strech is one of the most (if not THE most) important of the 12 basic animation principles of animation , the purpose of which is to give a sense of weight and flexibility to any animated element. It's also used outside of animation but I won't cover this.

In 3D CGI, squash and stretch is often obtained by scaling one axis in one way and scaling the two other axes in the other way, with a certain relation between the two scaling in order to maintain the volume.

In Blender, the only ways to do that, is either do scale up and down manually, or set up a stretch constraint with a target object. It's fine, but they both require quite some time to perform or set up. And the manual scale method isn't accurate.

Other softwares, like 3DS max, give us a manipulator which allows us to perform the squash & stretch on anything right away :

It simple, you use it like any other manipulator, and you can assign it a shortcut.

So here's the proposal for Blender : Creare a manipulator mode which does the same thing. It could be either an option in the scale manipulator (in which case it migh be nice to have a toggle key) :

Or it could be a different operator with it's own active tool :

It would be nice if it also had a different looking widget (whi not the scale widget but with spheres instead of cubes).

Note also that it should be possible to set a shortcut to this. Depending on how it get implemented, it would be a toggle shortcut (like if it's an option in the scale manipulator) or a simple call shortcut (if it is a standalone operator & active tool).