A lot of people have been theorizing that Jacob's Nemesis' statement of Locke's signature line, "Don't tell me what I can't do!" and the existence of Locke's memories inside the Nemesis is a sign that there's still a little bit of Locke inside of the Nemesis.
My theory on this: The little bit of Locke still inside of Jacob's Nemesis is derived from the Alternate Timeline, where Locke is still alive. We've seen many examples of our Losties having weird "deja vu" experiences in the alternate timeline, the most notable being Jack and Desmond's exchange on the plane in "LA X." What if this is happening to Locke too, and his consciousness is shifting between the timelines? It appears that Juliet's consciousness was shifting right before she died to the Alternate Timeline when she said "it worked" and "we should get some coffee." And what if every time ALT Locke's consciousness shifts, there's a little more Real Locke inside of Fake Locke in the original timeline? I think the timelines will converge when the Losties' consciousness shifts completely, and when Locke's consciousness shifts completely, he'll be back and ready to go on the Island? I have to admit, the idea of the real Locke inside the Nemesis, fighting, is one hand preposterous, but on the other hand, a really cool idea. Because preposterous is Lost's specialty.
What do you think? Good theory? Awful theory? Needs some work?