Locke DID have to die by Jason

This is my first time posting, however I enjoy reading the theories people come up with on here. This is obviously just a theory and I'm usually wrong. But I'll get to the point...

I believed, like most, that after last year's season finale, Locke was used as a pawn throughout the show by the MIB. When Christian told Locke he had to die to bring everyone back, I assumed like others that this was MIB manipulating him so he could use Locke's body as the loophole to kill Jacob. However, after watching LA X, my ideas changed. Last year, Illana asked Richard "what lies in the shadow of the statue?" Richard replied, "He who will save us all." Locke's dead body lies in the shadow of the statue.

Furthermore, Jacob approached Hurley last night to tell him to take Sayid's body to the temple. The Chinese leader of the others told him if Sayid dies they are all in a lot of trouble. Fast forward to the end of LA X and a dead Sayid wakes up to everyone's amazement and says "what happened?" Now I've read through some theories that say Jacob is Sayid. I disagree. I believe we will find out the real John Locke is taking the form of Sayid. Just a theory though.