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.