I don't care. If it wasn't in the movie, it doesn't exist. It's that simple. How many people will research the director's mcguffin motives vs. how many will see the movie?
For all I know, there could be tons of crazy ideas behind far better films that never made it into those far better films. In much the same way that I don't care at all about the personal lives of artists whose work I enjoy, I really don't care about the backstory inside a director's head that remained hidden there.
What still matters is what a shoddy piece of work Prometheus is ... though I suppose this points out how it could have been much worse.
