We've been trained to ignore the "are you sure" and just press yes twice when we press something.
Thus this button would be just a nice way to occasionally make a person lose 5 to 10 million gil.
We'd see one post each year from somebody insanely angry in the forum.
On the other hand we'd save a few minutes when upgrading from one fully maxed out set of gear to another, two or three times in a patch cycle... hrm...
tempting.