I'd like if moons were part of a planet and could be used for additional population and logisitc/tactial slots. If a planet has a moon you can research a (level 6 I guess) tech that permits you to expand your population to the moon. This grants you additional popuation that is immune to planet bombing, 4 logistic slots and 6 to 8 tactical slots. The moon orbits the gravity well of the planet itself, but at the outer edge (it also slowly rotates around the planet if possible). Of course the moon itself needs to be resized for that as to not look incredibly silly.
In order to show enemies that you have the moon research tech available the skin of the moon is changed to show artificial manipulation on the surface in the style of the respective race.
Unfortunately that's probably too complex to jut implement on the fly. Since asteroids and moons are more of the fast to take and upgrade and easy to hold earlygame spots that make for good chokepoints I'd suggest to make moons some sort of super tactical asteroid with beefed up tactical slots and/or less needed upgrades to unlock those tactical slots.
Edit: lol, using wail of the sacrificed from asteroids or moons. Well I guess since it's there anyways it's a way of softening the enemy before jumping in...
