I suppose this isn't so much a theory, more of a summation of the character of John Locke, as I see him...
MIB was involved with Locke from the start.
In terms of the chronology of John's life we have:
John tells Richard his birth date and birth location whilst in a time flash to 1950 something. John mentions Jacob and that he is the new leader of the Others (He believes this as he has just flashed from the point where Ben has handed him the baton and gave up leadership to John, telling him where his people are - John goes to them and FLASH).
Richard visits Locke at his birth in the 50s.
Richard visits Locke when he is about 6, in the early 60s. Richard notices the picture of the Smoke Monster attacking someone, as drawn by Locke. Richard tests Locke, what items belong to you - John picks the sand, the compass and the knife. Richard wanted John to pick the Book Of Law instead of the knife.
Richard sends an invite to Locke to come to a science camp (not) in Portland when Locke is in his teens. Locke was a man of science, starts to reject it.
Locke grows up, nothing of interest happens in his life until his mother appears, Cooper (Locke's Dad - do we know for sure?) steals his kidney. Helen appears, falls in love, struggles to forget about Cooper. Can't stay away, Cooper ruins Locke's chance with Helen.
Locke gets pushed by Cooper, breaks his back.
Jacob touches John right after he falls. It seems like he revives John by the touch.
John is in hospital - meets Matthew Abaddon who tells him to go on a walkabout.
John goes to Australia for the walkabout. Not allowed, goes on plane - 815 crashes on the island.
John can walk.
Journey of self discovery - looks into the eye of the island. Has visions. Gets into hatch, loses faith - hatch implodes, John loses his voice.
Back on track, blows stuff up - unstoppable etc etc.
Meets with the Others, is told he is special, Cooper is there, can't kill him so apparently he isn't the leader after all. He has Sawyer kill him Cooper - maybe he is the leader.
Ben takes him to 'Jacob's' Cabin, John hears "Help me". Ben tries to kill John.
John goes on a rampage, ends up being told by Ben - you are the leader of the Others.
FLASH. Back to the start but this time he flashes again and we follow his life onwards without going to his birth.
FLASH - Flocke is in this time. Flocke gets Richard to go to John, tell him he has to leave the island and die.
FLASH - John leaves the island after Christian who has frequently been seen in 'Jacob's' Cabin tells him he has to go by turning the wheel.
John wakes up off island with Widmore giving him a new identity and a guide - Matthew Abaddon. Abaddon is killed by Ben.
Ben kills John.
John is taken back to the island on the Ajira flight. Locke is now Flocke.
Flocke gets Richard to tell John to go off island and die.
Flocke gets Richard to take him to Jacob. Ben accompanies him in to see Jacob.
Ben kills Jacob after Flocke is found out to be Flocke and Locke is found out to be dead in a box.
So...
At some point in proceedings Flocke was able influence things to make John think he was the leader and when John went back in time he created his own legend by telling Richard he was going to be the leader in the future, this got the ball rolling and everything fell into place.
I can't figure out where Flocke FIRST influenced John to think he was leader. I was considering that it may have been when John heard 'Jacob' say help me - in actual fact (and I think most people will agree) it was Flocke who said "Help me". John heard this and Ben obviously didn't because he didn't think anyone was there - he was acting.
I also can't figure out Ben and Richard. They seem to be on Jacob's side but if Ben hadn't killed Locke then everything would have been fine - maybe this was just Ben's natural desire to kill John. If Richard didn't follow up on John's info about birth date and place, the legend wouldn't have had a chance to grow legs - was it just curiosity on Richard's part? These two things in particular seem too important for Flocke to rely on by chance happening, unless he has influence, or I have overlooked something...
Flocke must have had some more involvement that we haven't seen. He must also be involved with Widmore and Abaddon as it was Abaddon who got Locke to the island in the first place and Abaddon is working for Widmore, they were also there when Locke got off the island and had to die. But it seems the Oceanic 6 have to come back to help Jacob so maybe Abaddon and Widmore are helping Jacob with that seeing as they were helping John to gather them. This then makes it difficult to figure out who Widmore/Abaddon were working for when John became Jeremy because their actions throughout seem to suggest loyalty for both Flocke and Jacob...I'm getting confused!!!
I don't really know if this has made any sense or has come to any kind of point.
Hopefully this sparks some sort of debate and we figure something out.
Cheers!