I'm beginning to wonder if it's not the island itself that is going to be moved (again?), but the route to the island. It requires a very specific heading (325) to get to and from the island. Well, ok, we only know that it's require to get away from the island, but it makes sense that there would have to be a specific heading to get to the island.
If they change the route to get to the island, it would be the same as moving it wouldn't it? Plus, if there is anything in the ledger about the location of the island, it would still apply. Which is why Widmore still wanted the ledger even though the island has been moved several times.

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