Surely redundant but Metal planets?

I like the idea of Death Star much more than the idea of a metal map.

Why not have both?

a metal planet can be harvested or used as a weapon. however, harvesting does damage and causes parts to collapse etc.

Also: it would lead to some interesting battles i think. At one point, the guy with the best economy might just asteroid-smash it to prevent his enemies from out-producing them.

Keep in mind, if at any point your enemy starts to harvest the planet while you're on it you can overload the core, leading to a useless and very big pile of space debris. I imagine that it would break the planet to the point where there would literally just be unit-size fragments floating around.