The last act of Rogue One: A Star Wars Story (2016)

I would like to see some sort of prequel that takes place between ROTS and New Hope that focuses on Vader and what he was doing in that time between the two movies. It could expand on his relationship with Palpatine and Tarkin, lament on the loss of Padme, become more and more tyranical as the Emprie expands it's influence.