As you know, I've been going through the plays of Shakespeare. I believe that Henry VI, which I am nearly done with, would make an excellent space opera. It's a trilogy, and Science Fiction movies are naturally trilogies. The only change you would have to make is making every piece of Middle Ages technology into Sci-fi tech by adding the word "space" or "laser".
Space Henry VI retreats to his Space Castle defended by hundreds of men with Laser Swords and Laser Cannons. Richard, the Duke of Space York, lays siege with his laser cannons.
Now playing: Flogging Molly - Another Bag of Bricks