I know it's incredibly hard to make new zones for XI in 2025.
Abyssea showed how it was possible to add new zones without actually creating new zones, and sell mini expansions. You don't even need to redo the skybox, nobody cares about that.
If new 119 versions of Abyssea with other zones, this would be new content and mini expansions could be built around this if the will was there.
There are so many zones that are barely used and would get a whole new lease of life if reworked into Abyssea zones. This could be done for 5-10-15 new areas over many years.
Abyssea Vunkerl Inlet (S), Abyssea Reisenjima, abyssea Rolanberry Fields (S), abyssea Meriphataud Mountains (S), Fort Karugo-Narugo (S), adoulin zones, even bhalfau thickets etc. These could all be made into Abyssea gameplay zones.
The zones are already made, the gameplay systems are already there (just would need to level up the monsters to 119-140+), the maps are already made, the only real expense would be designing and creating some new monsters.
A whole serious of paid mini-expansions could be built around this.
I know it would be taking liberties with the lore a bit, but I think almost everyone would prefer new content over those concerns.
Also Assault zones are effectively dungeon zones, you could setup a bunch of trash mobs that players have to farm along the way to pop the boss at the end. The zones are perfect and under-used, Assault zones are effectively ff14 style dungeon areas that can be reworked into new content.