Well, as the main reasons for every suspect have been already said and explained, I just want to point some things that I consider vital for the investigation:
Red John is a guy with straight hair, middle-aged, good fit, who causes good impressions on women. Although lots of things point at McAllister, I don't really think he fits in that description. And the fact that he appears in the promo doesn't give any clue to me. The scene at the church, where he is supposed to be murdered, seems to be a quiet and calm meeting. In contrast, we see the sheriff running away from somebody, and I don't think that's the way PJ and RJ are going to meet.
My Red John suspects are Ray Haffner and Brett Partridge. And I must say I got really convinced by some of your theories assuming that the latter is the serial killer, but I don't understand something. When Red John gets Teresa at the first episode of this sixth season, it's obvious that Brett is tied on the floor. If he is the same person that gets Lisbon unconscious, she may be the dumbest person on earth.
With Ray, by the way, I can't find anything that makes him impossible for being Red John. The only thing that doesn't make sense is that he doesn't have the tattoo, but I think that's easily explainable.