John Locke in LOST2 has seen his LOST1 life. Maybe only in bits and pieces while asleep or unconscious, but he's seen it. He mutters his LOST1 lines in his sleep. He recognizes Jin in the hospital. He recognizes the words from his suicide note when Jack speaks them to him. I think he's made an explicit decision that he needs to go on with his life in LOST1 out of a mix of guilt and devotion to his father, Anthony Cooper.
I feel like the story needs to get Locke2 on board with whatever Desmond's LOST2 strategy ends up being, even if it's nothing more complex or developed than opening everyone's eyes to their other lives and loves. I realize there's not a lot of show time left, but I'd love for the finale to take place in LOST2's October and feature John and Helen's wedding.
This event, or possible the time leading up to it, would offer us the opportunity to have Detective Ford track Anthony Cooper down. In the process, he would confront Locke2 with Cooper's criminal activities, and maybe, maybe his investigation would reveal that at the time of the airplane crash, Cooper was likely "working" John to get him to give up a kidney for a transplant. Medically, of course, I'm clueless as to what kind of shape he'd be in as a crash survivor with a bad kidney, but I like this revelation. Locke would deny it at first, but Ford would leave him with a dossier (much like the one on Sawyer that Richard gave to Locke1) to review and the facts would eventually sink in.
Locke2 would realize that his guilt and devotion are founded on Anthony Cooper's lies. Freed from this weight, he could reconsider Dr. Jack's offer to "fix" him. If it's within his power, he might choose to discontinue life-preserving measures for his father. Heck, in a sweet reflection of LOST1, maybe he'd let Ford literally pull the plug on him.
But what this would turn him onto is the possibility of embracing his LOST1 life and the safety and protection of the Island, his Island people, and his 815 survivor companions and friends. I can't suss out the details, but I can imagine a crisis point where Locke2 is offered the opportunity to save the Island and his friends by agreeing to "return" to LOST1. Send his active consciousness and will across realities and into his living body.
Remember, Crazy Mother the Momster left a physical corpse, so these monster doppelgangers are indistinguishable from the original. If a disembodied—for lack of a better word—SOUL is seeking its home, and there is a dead and buried one and a perfect living copy, I say that it will arrive at that perfect copy, and the first order of business would be to kick out any squatters, namely, Esau!
This would be a pretty sweet part of the endgame, an internal struggle between Locke2 and Locke-ness, rendering Esau vulnerable in LOST1 on the Island, perhaps to an EM assault launched by Desmond.
And in the aftermath, when the *ahem* smoke clears... We see John Locke open his eye. We pull back and find ourselves in LOST2, looking down at Locke2, coming to after fainting at the alter at his wedding. Locke smiles as Jack and Desmond help him back up.
Then, we see John Locke open his eye. We pull back and find ourselves in LOST1, looking down at Locke-ness's body on the Island, and as Desmond and Jack approach him cautiously, he smiles and says, "I'm glad you believed me." When Locke2 returns to LOST2, the Locke-ness vessel is empty, but living. Locke1, one of the Island "whispers" since Ben killed him, fills the vessel and *BAM* The miraculous return of John Locke! If Jack accepts the Protector gig, then perhaps Locke becomes his Richard, or takes his rightful place as Leader. Of course, they're gonna need some people for him to lead, but whatev. They've got time.
Keep on keepin on~