here few suggest I throught of

timed mini dungeon these dungeon would have limit time frame they can be done in the give increase amout of exp and crystal and such

underwater dungeon these would be only access with fc sub, a airship dungeon access by airship. these more be limit picture a dungeon of assault an airship that been stole by pirates or a mountain dungeon.

set armor

people complain about no end game content well here few suggest in this fashion. I