The one hinted at the last live letter... The whole prospect of queueable content for the job in the pvp mode sounded amazing, and the idea of grabbing spells on the go as items on the map can be really nice, depending on how it's implemented.
Since they didn't confirm or deny if the idea was scrapped altogether or if they're still cooking the implementation, so there's hope for the next BLU update in Endwalker.