One thing that has not been done yet with FFXIV

[Illmaeran]

A entire zone underground, and a underground city player hub.

I hope that will be a thing with the Duskwight Elezens if they ever get a chance to shine one day.

As a Duskwight main, I would love to see Gelmorra open for more exploration outside of PotD and Toto-Rak.

[Denishia]

As a Duskwight main, I would love to see Gelmorra open for more exploration outside of PotD and Toto-Rak.

The real reason why I'm excited for the Criterion dungeons is because the first one is Sil'dah and we know that there will be more - and with how Agalia used the Ul'dah theme and ended its focus on the patron deity of Ul'dah, implying that the next two tiers will do the same for our other two Starter Cities - is that there seems to be a renewed effort from the dev team to return to under-explored Eorzean areas and history. And that the next most logical setting for the second Criterion dungeon is Gelmorra. Which also means escorting another NPC through it repeatedly and a decently lengthy side-quest.

The Tempest is by far my least favorite zone in this game, and the kobold mines most hated in ARR - but the Nu Mou caves have enough color and verticality, and Toto-Rak's revamp helped it.