My suggestion is that when you go back to your ship after owning a planet up this random event will happen where pirates will breach your hull and try to kill everyone on board including you. When you defeat these pirates there will be a chance of one of the pirates surrendering. You can then take him/her hostage and hold them for ransom. I think that this would be really fun and maybe if its possible you could board their ship and steal resources. Also (I know Im rambling sorry) you could join the pirate faction and get quests and stuff. Something like this maybe (not my pic btw)
I think this will be added into the game, but I would like to see some more info about these events in real game play. Would could be the worst thing that could happen? Or even all the events. Oh and love the picture.