Another that could be possible would be a storyline like on S.T.A.L.K.E.R: Shadow of Chernoble, only insted of one chernoble, the world, and aliens have taken over it, and those on earth left, or not in space, are left in a ruined world, trying to survive, you could join any faction, the remaining military, rebels, try to join the scientists, or just be by yourself, scavenging for food and clothing. And some people would buy stuff that is very valuable, but hard to get, like items in an Alien Hive, such as resin, or better yet, somehow get your hands on an egg. And in the very center of the huge free roaming world, is the main Alien Hive on earth, which houses the huge Empress, and the main story would be just killing her, while tackling side quests and killing drone aliens in the wilderness levels up your character so that he/she could kill the Empress. And when you get facehugged, you'll wake up in a hive, or, if your lucky, and you have people helping you, you can go to the scientists, and have them surgically remove the burster from you. If you don't have people helping you, and you wake up in the Hive, you'll wait until you get bursted, then load up your last saved game.
