In advance: everything that follows makes perfect sense in my head but may make little to no sense to anyone else. Sorry. Okay? Begin speculation:
Jacob and his “nemesis” (who will be referred to as the Man in Black from now on) are from ancient times (no idea when or from where) and they come to the Island (no idea how or from where). Events transpire that lead to them being exposed to copious amounts of the exotic matter that makes the Island so special. This allows them to see all of time.
For reference here I want to talk about the character of Dr. Manhattan in Watchmen. If you already know, disregard this section. So, Dr. Manhattan is a scientist who becomes trapped inside a chamber used for nuclear physics research, and is more-or-less dismembered atom by atom. He is reconstructed into a being capable of near god-like powers consisting of, but not limited to: superhuman strength, the ability to manipulate things at a subatomic level, teleportation, and an almost unlimited knowledge of the universe and its workings. But among all of these things he is able to do, the one that is most important to this theory is Dr. Manhattan’s ability to perceive the past, present, and future as all happening simultaneously. He sees all of time, but he does not do anything to change things because he sees everything as predetermined to happen the way it did and will.
So, anyway, what if Jacob and the Man in Black’s exposure to the Island begot a similar experience? They were able to see time as happening all at once (or perhaps, were just able to see the future of the Island?). Therefore, they saw everything that has happening in the past five seasons way back when. Jacob knows that the Man in Black is going to manipulate Ben and get him to stab him in the heart. The Man in Black knows this, also. One of these days, he’s going to find a loophole. Now, whether or not Jacob and the Man in Black share this information with each other is another thing all together.
Jacob says “it only ends once, everything before that is just progress”. Jacob believes that what he saw of the future and of time and the Island is predetermined to happen. That is why he is content with sitting around and weaving a tapestry (which is not to say it doesn’t look nice) for who knows how long, waiting for things to happen. He brings people to the Island possibly because he knows that’s what he does. Who knows?
The Man in Black, on the other hand, sees things differently. He thinks that just because they saw the future doesn’t mean that it has to happen. This is their feud, basically. He thinks like Desmond in “Flashes Before Your Eyes”; he realizes that he maybe he can change the future (although Desmond was tragically bludgeoned before he could put that theory into play). What he saw doesn’t need to come true, and so he is determined to prove Jacob wrong. Perhaps his desire to change the future manifests itself in other ways, maybe sometimes he just wants to prove Jacob wrong and show him that people are inherently evil and will just corrupt and destroy. Who knows? Maybe the Man in Black sometimes becomes the Man Made of Black and floats around judging people and instead of letting them duke it out amongst themselves, just kills them right there. Maybe the Man in Black just wants to escape from the burden of knowing the future, and this is why he feels so fervently in the! opposing viewpoint to Jacob’s.
Anyway, that leads into my interpretation of what the Man in Black means by “loophole”. Maybe he means that he will someday find a person who he can manipulate into doing his bidding (while rubbing his hands together and laughing fiendishly, obviously). But, if you look at it with the knowledge that he knows about the events with Ben and Locke in the future, that means (possibly) that Jacob knows the same thing. This could be why Jacob prepares his little A-Team of people featuring Howlin’ Mad Muhammad, B.A. BarJackus, and the rest of them who will remain pun-less. Perhaps this is not the loophole that the Man in Black is speaking of, if in fact he knows about it already. Maybe he is referring to something we have yet to see. Or maybe he saw something different than Jacob, and his visions of the future stop as Locke stares into the fire, and this is how Jacob is able to prepare his team without him knowing.
Something I just thought of while typing those hilarious A-Team puns: what if the Man in Black saw the past and Jacob saw the future? During their beach rendezvous, the Man in Black seems to talk about a lot of things in the past tense, making sure to mention how people ALWAYS corrupt and destroy, while Jacob seems to see things differently with his “it only ends once” and “anything else is progress” ideals. Perhaps the Man in Black is burdened with knowing every one of mankind’s repeated errors while Jacob sees that there will only be one end to it all and that everything that is supposed to happen will happen.
(Another thing I noticed that could just be inconsequential: Juliet experiences hoarseness when she wakes up on the sub upon her arrival to the Island… very similar to Locke losing his voice after the Hatch implosion. Maybe that is a side-effect of being exposed to the Island’s exotic-mattery properties for the first time [or in Locke’s case, in abundance]. Who knows. This is a totally different theory now, sorry.)
So, I don’t really know where any of this really leads to, all I know is that I was thinking about it and wanted to get it down. Thanks for any and all readings of this.
(All errors in speelling and grammar are intentional.)