considering all the hype about curiosity, i think that there should be mars rovers in this game. my idea for how they would spawn on planets depends on your home world. once you choose a home world, a rover (strength varying on your progression) will come knocking on your front door. with big guns. if you don't kill it quickly, many stronger rovers will land, until finally Curiosity him/herself comes! it may be to your advantage to wage war with the rovers because Curiosity drops valuable loot. ps. a few of their strengths would be: repairing self/others. strong weaponry. missile drops from spaceships. many, many different types of rovers(flying, tunneling, attacking)
So why would stronger ones land if you cant even defeat the first one? They would force you off the planet, making all the work you did to settle it worthless. Maybe if you die to it, it becomes slightly weaker for the next go around.
not sure about the idea but they should definitly try and put curiosity in somehow as an easter egg. i mean it is going to give us some of the most valuable information obtainable from an alien world. on top of the fact that everything nasa does helps further our technology substancialy.