How can I do extreme squash and stretch of a character animation? Example: A character is about to jump, his body is almost completely round then the jump now he's long and thin. 

I'm hoping I can do this in Blender and this is the idea I have.

I know you can't do this with great exaggeration with a bone rig so I have to delete the bones.

Transforming the bones deformations into shape keys for each frame then disable the armature. 

Then making a new armature with a single bone with a constraint that keeps volume, place it at the base of the character and that bone is weight painted to the entire character. Now I can add an additional animation step on top of the existing animation.

That is the only way I can see this happening. Is that the way to do it or is there something better to get this effect? Is this method the only way I can do this in Blender?
I believe this youtube link would help.
Blender rigging tutorial, part3

In this video, it is accomplished by setting an empty as a parent of the object and squashing it.