Here's an idea for the plot:
Leia goes to recruit Obi-wan, who insists on giving her a lesson.  Vader's ship arrives and Leia tells them to leave without them.  They find the Rebel pilot [@Shadow Daedalus] who's taking recruits from the nearby worlds to Yavin IV and fly with them.  They then take a ship to Alderaan. (Alternatively, if someone wants to play as Han or Chewie, they can hire a pilot to go strait to Alderaan) When they come out near Alderaan, they find the Death Star, with Alderaan intact.  They are caught, and with the planet as hostage they have to call for the Rebel fleet or take it out from the inside.