Speaking to Polygon, Vaughn revealed that the first film in the proposed trilogy was meant to take place almost entirely on Krypton, and focus on Jor-El and the impending explosion of Krypton. Though the alien planet would still face destruction, Vaughn and Millar's take would have the event take place much later in the timeline, allowing Superman to grow up on his home planet and gradually become familiar with Earth, maturing into an adult before having to reckon with his loyalty to both planets.
Though the negotiations Vaughn was reportedly in have since dissipated, the filmmaker didn't entirely rule out the possibility of returning to the DC universe. "It'd be hard to say no," he said, of being offered the opportunity to helm a new Superman film.
All I can say is... wtf? Glad this didn't happen.