I never went to Gusgen Mine alone in FFXI nor did I wanted to! That place was scary!!
Thus, I approve of this suggestion. We truly need strong ghostly touches in Eorzea, undeads are part of the lore too!
(at more than one place too -- ghostly FATE at night would be awesome too; the night becomes even darker, a thick ghastly mist appears, the music changes to deep horrifying tones... and bam! Ambushed by sneaky ghosts popping out of nowhere! ...or Slender men.)