Maybe add more to the BJ story?? Maybe the alien wants to try sex with a human. She likes it and she invites her sexy alien friend to join her and you get to have sex with both of them
Or maybe the leader is this sexy alien girl and you run into her while tryin to escape and she considers killing you but then has always wondered what sex with a human would be like.

The only purpose of that story is to be an example for the modding tutorial. There was a mod being worked on that expanded upon it, but I think it was more of a proof of concept and anyways wasn't updated for 3.5. I'm sure someone will make a mod that expands upon it eventually.