Dead is dead, locke is and was dead, which is a shame. But now we need to look at what we have also already been told already.
It seems that whatever Jacob needed to do or say to someone, he pretty much did it himself (as revealed in flashbacks) or by note (as ben says). Meaning in my mind that these apparitions of Locke, Christian etc etc were all the work of his rival. Which would have to link him to smokey. And now i believe that the man inside the cabin who asked Locke to 'help him' and the man who said move the island was that of the rival, and not Jacob. But one thing gets me is that, say smokey is the rival and smokey protects the others, why would the others take orders from Jacob. Given that smokey and Jacob are at war, they cant be.
I would want to say that the rival manipulated events in order to cause the incident which through the oceanic flight crashing etc, results in Ben killing Jacob. But that doesn't explain why Jacob interacted with everyone and told Hurley to board the flight.
No clue whatsoever who this rival is, but his ruins are deep within the jungle, and Jacobs place is by the sea. Or at least that's how it seemed, like Jacob came after the rival maybe, or was pushed to the edge by his rival. And i want to think that the rival is the Island. Note at the start how the rival goes back into the jungle and leaves Jacob on the beach. I wonder if Jacob has even been into Island or whether he just lives on the coastline?
So maybe there's three people here. The Island, the Island's Bodygaurd (smokey), and Jacob. The Island is using it's bodygaurd to get rid of Jacob (the outsider). Who had managed to manipulate a loop through time which gives him power of sort, which at this moment seems to just only be longevity.