I was reading and I was thinking about how to redesign Captain Marvel, something I've been pondering for a while. As I was reading (before I got to the time travel bit) I thought "Wouldn't it be great if Captain Marvel was just Billy Batson from the future? And Shazam was just Billy from even farther in the future?". Then as I was reading about how the Rock of Eternity was at the beginning of time, where all of time and space existed at one point, I thought "Wouldn't it be great if Captain Marvel pulled a Promethea style move and destroyed the physical world, rejoining existance into one piece. And Shazam not only lives at the beginning of time, but the end of it also?"
Now notice what Captain Marvel says later: "I must confess, there are blank spots in my memory". Hmmm....