Why Lionel specifically? Because the USRA Heavy Mountain and the USRA Light Mountain had the same size drivers, and cylinders that were just one inch different in diameter (could be ignored on the model), and Lionel has already produced a beautiful rendition (if you can ignore or change the Olympic broad jump, engine to tender) of the USRA Light 4-8-2.
"All it needs" is a new, brass, fat, imposing Heavy 4-8-2 superstructure put on the existing running gear. Even the valve gear is Baker on both, and I believe that the tender could be used, too. Think USRA Light and Heavy Mikados that Lionel accurately did - similar situation.
There were not a bunch of these built as "originals", but they were copied more than once.
They are also generic-looking enough that Lionel could offer them as "near enoughs" to some big locos, as they did with the USRA Light Mountain.
Also, as they share the running gear with the Light, they would be able to take the same curves and not need 072 or the like.
I'll take one.
USRA Light 4-8-2 - handsome:
USRA Heavy 4-8-2 - handsome-er:
