I think the cabin is actually symbolism of the island..(and more)..
A man was trapped in the cabin...just like the MiB was trapped on the island
The man in the cabin didn't have a physical body that we know of...MiB said Jacob took his body (or something along those lines)
The cabin seems to move around the island and isn't stuck in one spot...we know the island moves around too, in space and time.
There was a circle of ash around the cabin...perhaps stopping the MiB from destroying the cabin? or from leaving the cabin?..the circle of ash could be symbolic also, the cabin is either protected (like MiB claimed Jacob protected the island)...or the cabin is a prison (like the island seems to be for the MiB).
What does everyone else think?