This treatment is sorely lacking two things... drouds and aliens.
ALIENS:
Both the Tatooine barfight scene, and the massive trading post of Oxus would be great places to have lots of alien races interact.
DROIDS:
I think the best place to add a droid character would be for King Kaylos of Aquilae to have a personal valet-droid, who then serves the new leader of Aquilae in the final scene (helping the audience identify some new character as the new king).
Also, I think it would be cool if the Larses had a totally broken down droid (one arm, eye lights that flicker) that helped around the farm and talked with a broken voicebox. During the shootout with the Outlyers it could buy the farm.