You know how Vegapunk tried to build the island-heating sytem for Karakuri Island, but it was incomplete, then Franky blew it up? What if Franky felt bad and rebuilds the thing so that it heats the island and so that the people aren't mad at him anymore?
Also, on an off note it seems kind of wierd to me that all of the Straw Hats were able to get back to Saobody Archipelago so easily. Even if they have the Vivre Card, they still have to go through a large portion of the Grand Line or one of the other oceans to reach it. Just a thought.