[medved]

In an age of carbonfibre tennis racquets and ceramic tank armor, it's not at all obvious to me we ought to be building skyscrapers out of concrete and steel anymore. You might could figure a way to prefab individual levels out of very light and strong stuff and simply stack them on top of eachother and have the whole thing back up in six months.

[giotto]

If the floors hadn't pancaked, only the part above the fire would have collapsed. Instead of stacking floors, why not stagger very long steel bars, like the irregular support structure of a tree? So if there ever was a meltdown, the worst it could do is crack unevenly like a branch.