Twist at the end should have been?

Movie would have been a lot better if it were revealed at the end that one of the dad's were a demon of some kind who know that the showdown at the cabin was going to take place in the future; so he kills either of the dads and takes his place. His job would have been talking the other out of making a choice until it were too late.. Once the final Horsemen kills himself, then the demon reveals himself to be working for the Devil and he had successfully brought about the end of the world.. The other then begs the demon to kill him to prevent the apocalypse.. But having fulfilled his mission; he just smiles and walks off into the woods and everyone on the planet dies...the end. I like when the bad guys win some times..