I know that Mel, George Miller (director of MM), and I think Bruce Davey spend many hours in George's kitchen developing a story line. I'm sure they had a few angles on the plot.
Sure wouldn't hurt to drop Icon a line, and put another bug in their ear!
George Miller is a cinematic genius. He's only made 6 films and all six are masterful (3 Mad Max films, The Witches of Eastwick, Lorenzo's Oil and Babe:Pig In The City)