Actually, you could place a bomb up there, then drop it through using Danger. And you can even have it land on the iron box and push it left so it actually gets used meaningfully. So there's another thing for Completely Destroying The Game Using Excess Bombs.
You know, I wonder if there's anywhere you can blow out into empty screens horizontally, because those sides aren't blocked...
EDIT: Looks like if you could blow rightward out of Area 5 somewhere (5-3? 5-8?), you could drop into 6-1 and have no trouble because that level doesn't require limit-broken spells, and limit break gets set in 6-2. Leftward doesn't seem to work - there is technically an opening, but you can't remotely make it.
And now I'm wondering if there's something absurd you can do with Berserk and the fact that exiting left/right/up will "prevent" the other girl from exiting down...