Metal planets- a Subterranien layer?

Well of course they'd be a game ending weapon capable of destroying planets, why else would you build a planet?
But other than that, having a subterranean area would be baller as all hell, but probably a bit strange.

Personally I do not want both the killer planet and the subterranean battlefield.

I love the idea of taking over the metal planet, it shouldn't just be "You failed to take the Metal Planet... GG" they need to be able to be taken out or at least disabled.

Easiest way would be special hardened power plants that only a commander or T3 engineer can build and you have to build them at certain points on the Death St... Sorry Metal Planet. Give the Hardened Power Plant a high cost and the chance to go nuclear if destroyed

I think this is only really whats needed for Metal Planet control. Another layer while it would be interesting as someone who used to love playing Metal Fatigue the thought of having to clear an entire planets underground layer as well as the Land, Sea and orbital, and then do it again on the next planet is just so bad its wrong, unless your the sort of person that likes spending copious amounts of life in one fight...

For anyone really wanting to play underground, go play Metal Fatigue put the hardest bot on you can, after you've beat it (If you don't, lower the difficultly and try again until you win) try to think how quickly you beat them on the ground and in the air but how stressful clearing the underground level was, unless you got lucky and the AI didn't go underground at all but then congratz you either hacked or got so lucky its untrue.