I think that the planets should have some rare ore on them like diamonds but are more common on some planets but on other's it could be a different ore im not sure what kind of ore but some kind. or there could be like super rare spawn's which is like a giant moon cyclops or something and it'll be huge and could like blow a hole in you base or something or rain meteors on you and it would be different for every planet. this would just make the planets have something on them to hunt/fight.