While this isn't quite related to the story aspects, having the ability to manually "level down" your elemental level in Eureka is a change that has long been overdue and should've been added before Stormblood ended, simply for the fact that if you have a friend trying Eureka well after you have, you cannot party with them or you destroy their ability to gain elemental XP. You can still play with them and smite the enemies they claim without being in the same party, but it's such a janky solution.