[Puke]

i dont think emmissive or regular armor abilities work on planets. you can use either the shield or phased shield abilities. if you use phased shields, then shield-skipping weapons wont go through them.

sadly, this has the drawback of leaving them vulnerable to shield depleting weapons. otherwise, it is functionally the same as armor.

Traditionally, if you just want to add alot of hitpoints to a planet, you can build weapon platforms with nothing but armor on them. Or perhaps design a special size of weapon platform that takes a special armor component that is too large for regular weapon platforms.

If you want it to occupy facility space, you can always build cargo facilities on the planet to hold more weapon platforms.