Jacob's Nemesis really a Nemesis?

Hey guy, here's a theory I came up with today. Is Jacob Nemesis really a rival to Jacob? I was just thinking we know so very little about this guy, and we've only really been aware of him in two scenes (Finale opener and Ben-kills-Jacob scene), and know so very little about him, almost nothing. If you watch the finale opener again, up until the "do you know how much I want to kill you" line, J.N. and Jacob seem to be almost friends. And again in the second to last scene, the two of them seem to be talking somewhat pleasantly to each other. Maybe they are in fact "friends" (in some term of the word)? What if Jacob needed to die for some reason and take a new body (Frank?)? Now, I admit there are some major holes in this theory, and its probably a little far-fetched, but its an idea, and I'm not supporting it or fighting it, just wanted to see what other people thought.