Give it a go. That sort of change is more likely to result in a better re-write of the story than anything else I can think of. Put it back a level and you'll notice that Brom-iwan Kenobi suddenly becomes a villainous figure. More focused on indoctrinating the kid into his army than on training a new dragon rider. It puts the whole conflict between the rebels and the empire into a background distraction. A pointless conflict purely to weaken and divide the other races. It very quickly becomes a very different take on the standard fantasy setting and plot. After all, what changes when magic itself becomes both sentient and evil?