You are missing the reciprocal nature. Of course what I said is highly simplified and stylized to make the needed point. Curt, you are trying to use the same energy over and over again, and it doesn't work that way. There is only one store of energy in this problem.
If a bullet cuts a clean hole through a wall, the bullet stays relatively intact. If the soft bullet splatters on the wall, the wall stays relatively intact. There is a reciprocal nature to collision damage. The total amount of damage is given by the energy directed toward it. The damage can be shared between the two objects, but cannot be increased by imagining that one object is demolished, then turns around and demolishes the other one.
Yes, elastic collisions can occur. This complicates the problem, and is further proof that the "collpase" theory of 9/11 is false. Any elastic collision will not pulverize material either.
For instance, hundred ton chunks of steel were thrown sideways 600 feet. It's plausible that this could have come from GPE, but would require a bounce. That is, an elastic collision. Again, this requires great resistance from something. What? If all of the lateral motion is the result of elastic collisions, what is providing the resistance?
How can this tower demonstrate such high resistance, and such low resistance at the same time?