I dig it. I saw some inflatable packaging a few years ago that had a clever one way flap (valve) that allowed you to easily inflate.
How about a stackable paper-pulp egg-crate design? Aligned one way it stacks tightly. Align any other way and it becomes instant filler.
I hadn’t considered the “nested doll” storage option–but we all do it.
I wonder if standardized box sizing would help the situation?
If weight was roughly known, this might also help the ship-back issue–thats one of my gripes about shipping auction goods from home. I’m not “professional enough” to own a postage scale and meter, but if the original package had a standard size/weight/cost associated with it, automatic-postage (via the web or charge-back) would be built-in.