I can already guess the plot - Set in Coruscant, the main plot would some Jedi survivor stranded deep within the dark bowels of the new Imperial capital trying to escape, along the way picking up a band of allies consisting of gang members/aspiring spaceship pilots he/she picked up along the way, and in the process had to contend with some dedicated/ruthless Imperial pursuit force, the interstellar criminal world (e.g. The Zann Consortium and the Hutts) and a lot of manipulation and fighting in between. Chances are that the plot evolving into a rescue of influential/famous Star Wars characters who would later become core members of the future Rebel Alliance (e.g. Mon Mothma) is inevitable. Oh, and if a Jedi is concerned, he/she will die via sacrifice. Emperor Palpatine / Darth Vader and other major Imperial figures may or may not get involved.
No, no more Jedi survivors, please. Coruscant is crowded with them as it is with the Coruscant Nights trilogy and all that. It starts to stretch out the suspension of disbelief if every Jedi John Doe around managed to evade the Purge. Besides, the Prequels were all about the Jedi. Maybe the common man should be the focus this time?
Side plot would showcase the Empire's systematically take over, portrayed step by step, and how the support slowly crumbles away as the people realizes what being Imperial meant, witnessed from the eyes of either a initially loyal Imperial official with a conscience or some near-human alien average citizen who initially supported the Imperial regime. The side characters eventually become disillusioned and horrified with the Imperials, perhaps later becoming wrecked with guilt for doing something horrible for the Imperials at one point. The sideplot would intertwine with the main plot at one point, with the side characters' actions becoming critical to the main heroes' success, and ends either with the side plot characters getting killed for their involvement or the movie ends with them hopeful that their efforts are not in vain and it would help bring about the fall of the Empire.
See if one could throw in some other often ignored but crucial characters, like Kyle Katarn, Han Solo, Shaak Ti or whatever.
Just a hypothesis. How's that?
No Solos, Katarns, Tis or anything like that. They have their own adventures and rather extensibe background already. New characters would be preferrable, whose fates are really hanging by the thread. We already know that Solo is going to survive so it would kill much of the suspense. Same for Katarn etc.