You know you want one there.
Just add it as a rare (and since you recently changed a couple Korthos quests, we know you can add another basic room to the waterworks).
My idea for this:
Very young green dragon (ie, not a big dragon). This can be accentuated by placing the dragon by a large, hatched open egg.
Maybe make it a bit of a challenge, but nothing a FULL party of newbies couldn't beat. Vets would still probably be able to sneeze and kill it.
Chest:
Random generated mostly
small chance at Green dragon plate, green dragon hide, or eye of the hatchling.
Green dragon plate:
(unbound)
full plate (normal stats)
+1
exceptional acid resist 5
false life
Green dragon hide:
(BtA; exclusive)
leather (normal stats)
+1
exceptional acid resist 5
dragon haze: green hue around user (counts as blur, lasts 30 seconds, one use per rest)
Eye of the hatchling:
(BtA; exclusive)
trinket
greater corrosion II
lesser acid lore III