I haven't done a campaign proposal in a while, and with the upcoming July release of Fantasy Flight Games's Edge of the Empire, well, Star Wars has been on my mind. Now, unfortunately, the "last of the jedi" source book that FFG is planning to release won't come out for another two years, but I still think it would make for a very interesting campaign if done right, and it's not like it is a plot idea that needs a specific system to work, right? Any Star Wars system should do. Heck, even FATE should work.
Obviously this would be a Star Wars game.
The PCs would be high level, preferably primarily jedi, that are on the run for their very lives. Non-Jedi PCs could be allowed, just making them 'war criminals' or something, but for the full effect it'd be best for this to be a primarily Jedi game. Besides, this way you don't have to worry about Jedi being unbalanced or over powered since everyone in the game is a Jedi.
The game would take place before A New Hope but after Revenge of the Sith. Whatever you want to say you feel about the prequel trilogy it still gives us a time frame. The Old Republic has given way to the Empire. The Jedi have been purged and the new government is doing all it can to both spread lies that the Jedi were charlatans using tricks to maintain power and that they had attempted to usurp power. Essentially, that the Jedi were just folks who made a try for power and failed. Obviously Vader and the Emperor know the truth, and they also know that the Jedi are the only real threat to them so they're doing everything they can to wipe out the remnants of their one time allies.
WHAT Pt 2.
Now, the crux for this game is for the PCs to be trying to survive, however there needs to be more to it than that. The Jedi stood for something after all. They had an obligation to be peace keepers and to protect the innocent, and along with the Empire's rise is also the subjugation of non-human races and the setting in of xenophobia. This is a dark time, and champions of justice are needed more than ever. Can a Jedi simply stand by knowing people are suffering? If so, are they really Jedi? How about the fact that they're being vilified en masse while simultaneously being made into simple folk lore?
Ideally I'd like to start the game off during the clone wars. You do the intro, establish the characters as Jedi Knights, and maybe get them to be high level knights or full on masters by the time the Clone Wars are wrapping up. Introduce ObiWan, Anakin, Yoda, and several other fan favorites. Then you have the purge. The betrayal in the field of battle - maybe have the PCs all at one big battle - and the rise of the Emperor. The group gets the signal from Coruscant to regroup at the temple, but en route it changes telling them to flee. They hide during the formation of the Empire...maybe do some good in the outer rim, but then hunters start showing up. Eventually, perhaps even force sensitive hunters as Vader forms his little faux apprentices and the Emperor trains his right and left hands.
Eventually either the PCs make an attempt on Vader/the Emperor and fail horribly setting up the canon of the movies for A New Hope, or they join up with the alliance and help as they can altering the world line into one where Luke isn't the last of the Jedi even if he is the one who can confront/beat Vader, and Vader is the only one who can defeat the Emperor.