I found the Zilconis bit to be creepy as hell. Dragon eating naked girl... no, it's not rape. Yes, it's very rapey.

Anyway, my first thought about Natsu's plan was the whole "get eaten and beat them from the inside" bit. Then I thought, "Or, it could be to eat the dragons." Do we know what elements the different dragons are?

Zilconis: Air-based (presumably)
Atlas Flame: Fire-based (duh)
But what about the others?