I'm interested in what his training background is. It would, in my opinion, take a very agile mind even to borrow techniques from other disciplines to assemble some sort of system. What I'm trying to say is that some training, or at least some physical experience of grappling or fighting techniques seems, in my mind, prerequisite to putting together a new way of approaching things.
Kano was trained in Jiu-jitsu before he experimented with new techniques.
Rolls Gracie was heavily schooled in his family's grappling style before he revolutionized BJJ.
I absolutely have the utmost respect for Greg Jackson; he is a top-notch professional and seems like a cool guy. I have a hard time believing that he came up with a system with no formal training, though.