I had idea that I thought sounded pretty cool. At least to me it does. Not sure how this would work in practice but on paper i think this sounds cool. Make 14 slightly less linear. To open the main story up to be influenced by the players. Have some key moments in the game that can effect how the over all story unfold. Give players a choice at choose to be a Warrior of Light, or a Warrior of Darkness. The key moments could be for instance Raids. Which ever side beat their raid first effects the story into their sides favor. Which would make ever servers story slightly different from one another and give the game a huge amount of replayability. I'm not a pvp person so if something like this ever happened I'd like them to stay away from turning into pvp, faction vs faction like a lot of the other mmo's.
So basically it be like having a general layout for a story. With 2 different endings. We as the players have a hand in determining how it gets to either of those endings; and which ending we get on our server.