I'd rather have it be a mistery/thriller plot involving some elements from the past, thus having the investigator (Luke) revisit places from the OT, probable looking for something Vader left behind. On his way, he could find young children strongly sensitive to the Force. As a secondary story, the New Republic is being reorganised.

And I strongly believe in the end it will be something like that, because it's the first movie of a new series and they will have Vader be present somehow as a reassurement. They won't be totally revolutionary. Besides having Luke get into his father's life is character development and fan service at the same time, and above everything, it would be a movie middle-scale as the OT is, not the super-grand-epic-213612876389127 warriors-running-the-same-way the PT is, and full of nostalgia for the Empire era.