Bump.
I would want a mear graphical moon than looks nice and orbits properly. However if it can be done better, i think the easiest way of doing it would be changing an metal/crystal astroid into a moon, set it to a path (if they can be made to move) around the planet, and from that you could use the menu for building a mine, (create new upgrades available only to this object). But then the question is WHAT should you be able to build on it (i think 3 choices with one slot- reaserch lab (+10% to both domestic and military research rates - to keep it simple), lunar factory (+10% to construction spead of buildings and ships in that gravity well), and military base (+6 logistic and military slots/points for that gravity well). For the random chance of a planet have a moon, there are random chances for a planet to have an artifact or planetary bonus, it could be included there (but you dont have to "Search" for the moon to notice it"
But yes please... even if its just a mod to the planet graphics to have an inert moon. It just seems like somethings missing... and there is...