Given my in-game recollection, I'd bite on Bullet Seed being floor 1. Bullet Seed probably is enough to boot, given how frail Rampage Drive is, and you have someone who starts with Defense buffs and infinite healing. I suspect Rampage Drive may not even be immune to statuses (P3 Tartarus bosses loved to have those odd holes, particularly in the early game), which would keep things handily under control. Transform could also work if you could convince people it was floor 1, which is hilarious, though (RD has magic!).
EDIT: I keep having the nagging feeling this may not even matter a whole lot, since I'm thinking there's some Mew clause I'm forgetting for dungeon purposes, but damned if I can put my finger on it.
EDIT 2: Hmmm, Mitsuru's healing is never really bad, although she's stuck with ST. She covers status poorly (P3 status is inaccurate as all get. Marin Karin is particularly horrible, something in the house of 30%?), her selling point being the magical offense (she's also pretty MT-centered offensively, which is pretty sweet. Tentarafoo, while inaccurate, is early MT silence, which could be useful -anyhow-, even if in the 30%-40% house for acc.). The weakness can be amazingly nasty, though, it shocked me to see how often Persona elemental weaknesses have come into play in the dungeon so far.
EDIT 3: Rydia... mmmm. She solves the Rampage Drive issue, but is inferior to Rosa as a pick across the board, and those first two floors will be murder on her (she starts out terrible, status aside. Also, I have to wonder about Hold's accuracy, since it's about the only non-Sleep/Piggy status in FF4 that hasn't got accuracy hype). At least Mew can soften the blow there, given Firefly. I'll confirm with Neph the Rampage Drive thing first before definite assessments.
