It always annoyed me how interesting the world looks but it feels like a cardboard model in the end. Outside of FATEs and some one-time quests, there isn't much happening in zones that look quite interesting when you fly by. So I'll support any idea that brings life to these maps.

-Having played GW2, I would have loved to see the FATE system in this game creating a similar effect. Like, losing control of a whole town or changing the mobs in the area based on the results of it. For this, the rewards must be increased as well, as exp is no longer needed at max level. Maybe they can drop some sort of extra currency. Hunting seals come to mind and whatever they want to implement in the future.

-Stealing the idea from Eureka: Treasure maps can randomly drop untradeable carrots, which will summon a rabbit upon use, leading you to a treasure hidden somewhere in a random map (Coerthan rainbow carrot, La Noscean rainbow carrot, Hingan rainbow carrot and so on). These chests can hold fragments of a map that can be traded with an NPC, say 4 pieces to get a map. It would lead to a location where you can find a portal akin to the Canals/Aquopolis.

-Writting about the fragmented maps, I couldn't help it but to remember about chocographs. Maybe we can give our chocobos a "dig" option and have these hidden in the overworld map.