For this game, they need to add more open world content simply designed for spirit bonding equipment for materia. This may be alleviated with expansions and zones with higher level open word mobs, but right now creating materia is far to time consuming for high level equipment. A great way to expand the open world would simply make dungeons "open" after clearing the missions. This would add like 20 new zones to explore... Tho they would need to open up all of the side areas in the dungeons that appear closed off on the first or even second runs with the hard mode dungeons.

Once dungeons are open they can then add all sorts of quests that could be repeated for the money of the day or week. And maybe rare monsters that are actually difficult to get to solo, with special drops. Can even make new treasure maps in dungeons with rooms that lock when you open your chest or something.