I've been thinking...does Thanos really have to be the villain of the film? It would be weird if the big baddie they gave us at the end of Avengers got beaten in a film before Avengers 2, if that happened he might as well be Loki level. At the same time, it wouldn't make sense for the Guardians to lose in their debut film either. Then I remembered about Adam Warlock and that storyline with him and Gamora involving the Universal Church of Truth where Thanos teamed up with Gamora to take down Magus and the Church...only to back stab her in the end. If Warlock is in the film, it would be a good use of his character to have his alternate self as the villain while introducing Thanos as a conniving, hands-on bastard. It would also be a good way of showing all the different aliens in the Marvel cosmic, through the church. The church was even used in the 2008 Guardians comic.