These are a few thougts i had to write down
(im am writing this on the premise that the ajirra landing is exactly 30 years after the second jack-jungle-waking-hero thing.i personally dont like this approach but i think its likely they took it. also english is not my native language so please forgive me my misspellings.)
traveling to and from the island as timetravel:
timetravel of ajira flight is caused by a timegap between the island and the rest of the world, which existed alrady by the time the freighter got to the island and seems to be widening. possibly caused by the swans implosion. but technicly this would not be timetravel in the strictest sense as there is only one time to travel to. if for instance somebody went off the island to get winning lottery numbers and then go back to the island, they would have them before the actual lottery takes place, but unless they play with the donkywheel they only could go to times after the actual lottery.
the possibility of MIB posing as Jacob off island:
at the point at which jacob appeared to hurly he was, per date already dead, so mib could use his body to appear to hurly so the flight could go back in time so he could kill jacob so he could appear to hurly so the flight ....
the possibility that MIB did not leave the island (in which case the appariations of christian, charlie and claire ... hmm many c's here ... would have to be explained somehow else):
flocke appeared only after sun and lapidus met christian so it could be that the changer never went off the island at all.
the touch of jacob :
john, jack, kate and sawyer met jacob before they went to the island and he interfered in a way so they would become the persons they became. hurly and sayid met him only after they got off the island. and he interfered in a way that would ensure they would go back to the island. he blatantly told hurly to go back and made sure sayid would have a reason to kill a man so he would not put up much resistence in his "arrest", try to think what he would have done had he thougt illana would bring him back to the island from the beginning and on purpose. which brings me to illana. the scene between illana and jacob i find quite odd. It seemes to me as if he bribes her with healing than do so and then ask for a favor. Its more like "do or die" or faustian bargin if you want. also we dont no when this happens. most likely shortly before the ajirra flight but could be long before or after.
thanks to all off you for many great hours of theorizing over your ... well theories.