3. Darth Plagueis
The Tragedy Of Darth Plagueis the Wise is a huge part of the Sith lore. This wealthy elite was obsessed with eternal life. Plagueis experimented with ways to cheat death and create new life from the midi-chlorians. He also trained Darth Sidious in the ways of the Sith and the dark side of the Force. Sidious became convinced that his master had outlived his usefulness, and eventually killed him in his sleep. This is told as expository dialogue in Sith, as Sidious later recounts the tale as The Tragedy of Darth Plagueis the Wise to Anakin Skywalker.
Why Make It? Plagueis is a good test that could be used to measure the success of SWEU heavy stories. The novel, while a good read, doesn't have to be the total source material for the film either. It is so vast that this would be implausible to produce a 90-minute compelling film. Rather, it could follow the training of Sidious and his interaction with Plagueis; complete with epic duels and other training that would be laced with discussions of the nature of the Dark Side. (in a twisted mirror of Luke's training with Yoda in Episode V).