As well as sightseeing there's also:
Side quests
Hunts
FATEs and their chains, plus the super FATEs.
Gathering
Treasure Maps

There's plenty of open world content to do. You just don't want to do it.
Anything else they add in, you also won't want to do. Because no matter what it is, it won't give endgame gear or be an optimal source of tomestones.