Keep in mind that obsidianizing magma is also a method of infinite stone. Sadly, goblins can no longer bring you infinite goblinite unless you use DFHack to spawn infinite waves or something, but in general, metal is reusable if not recyclable. Steel armor can be passed down through generations of dwarves if need be, so only bolts are in need of replenishment. Fortunately, I think bolt splitters and melting still works as an exploit to gain infinite metal while also training your marksdwarves in the process. Hence, a player shouldn't ever have a situation where they've literally exploited everything in their entire embark unless they're going completely out of their way to do so, or you started in a metal-void embark to start with.
The only reason, therefore, you'd really want to do this is for realism's sake... but meteors being drawn to strip-mining operations is not realistic, now is it?
What would make more sense is that if you excavated a truly massive amount of land, the surrounding land would either collapse in on the massive sinkhole you dug or the reduced load would cause a slow-scale eruption of magma that would replace the crust you took off the land with fresh basaltic stone. (And when I say 'truly massive amount of land', I mean cut holes many tiles across from the surface down to the semi-molten rock.)