Well, that is sort of how John got to be a GL... he was chosen as the alternate GL of Earth. Guy Garner was the original choice to be the alternate, but then he was injured, so John was selected. It is important to note that it was this injury that caused some minor brain damage to Guy and that's what turned him into the frequent ass-hole that he is today. But yeah, if they were going to do a GL film with John as the main character, your idea would probably work best. I wouldn't be opposed to a movie with John as the central GL, but I do think Hal should at least be mentioned or appear and should be established as the greatest or one of the greatest Green Lanterns. Of course, I would prefer that he is the main character, but as the Rolling Stones once said "you can't always get what you want, but if you try sometimes, you just might find, you get what you need." Thus, if we got a GL movie with John, Guy or Kyle as the main character and not Hal, but the story was taken seriously and it was well-made, I'd be happy. As long as Jack Black (or any other actor who relies grossing the audience out to hide is miniscule acting talent) isn't in this movie, I can live with it.