I think they need to add a world event that can be easily modified.
Any new world event needs to be more valuable and profitable than the last or no one will care about it. This has led to things like the OG fort being absolutely abysmal in terms of loot.
They should definitely give a little buff to OG forts in terms of loot, like an extra stronghold chest or bone dust. And FoFs should be one cycle of captains shorter, just to make them less of a chore.
That being said, I agree that a new world event would be nice. However, it should be modular in nature or something that be modified easily to spice it up.
Because of commendations and such, the world events need to be frequent enough that you don't only see an ashen winds every 20 hours. World events are also some of the coolest things in SOT with some of the best game interactions in the history of the game. Adding more is always amazing. However, having 15 world events would be terrible.
Hence, why I'm suggesting that the next one be customizable, either to be updated by Rare periodically, or for players to choose its features in-game. Something like how fleets had only firebombs and cannons at one point an no cursed cannons but on a more complex scale. I'm not sure how this would work exactly, but events that can change over time is the only way we can get events in the future, because there IS a soft cap on the amount of world events that can be in cycle.