This ffxiv dungeon would be 100% pitch black

FF1: Temple of Chaos(bosses: 4 Arch fiends, also Tiamat could summon Warmachine!, Final Boss: Chaos

FF2: Pandemonium/Jade Passage

FF4: Tower of Babel(might be too similar to Binding Coil of Bahamut), or Mist Cave...fighting a version of Mist Dragon could be fun, mechanic-wise.

FF7: Temple of the Ancients...could have some fun puzzles...also fighting a boss on the God of Time (giant clock bridge with moving hands that knock you off, forcing you to move constantly as you fight while avoiding falling off the hands!)

Boss: Demon Wall, but this time instead of edges on the side, it moves closer to you until it crushed you against the back wall.

FF8: Temple of the Unknown King, could face you against Brothers Minotaur and Sacred

FF9: Inverted Castle. This could be a dungeon where strong is weak and weak is strong like in FF9. Low level weapons are powerful while strong equipment is weak, furthermore, high potency attacks are weaker than lower potency attacks.

FFT: Midlight's Deep. This ffxiv dungeon would be 100% pitch black, your wouldn't be even able to see your characters except when highlighting them with cursors. For every mob or boss you kill, the dungeon gets incrementally brighter, but it would still be quite dark. There would be traps that when walked on would inflict stacking debuffs just like in FFT (examples: Poison trap/petrify trap, maybe a steel spikes trap that degrades equipment, or traps that reduce built up brightness, making the dungeon darker again). Bosses would be much harder depending on how dark the dungeon still is by the time you reach them(would have stacked buffs, granting them increased stats and haste). Bosses could be difficult FFT mobs like Dark Behemoth, Elder Treants, or maybe groups of Humanoid monsters modeled after FFT characters or classes?