
This is a slightly edited version where the Outer Wall has been shifted to where it's supposed to be. Hell sticks out and the Balcony doesn't reach, but that is right where it's supposed to be - the top connects to the little hallway with Itoh, and then to the near-bottom part of Plantation.
Also, where did you get the idea that the Balcony is
supposed to cover the entire island's surface? Forgetting that this is all our interpretation of where things should be, the name itself suggests that it is simply a balcony area on the edge of the island, and the building with the Demon Crown is on it. Certainly beyond that building there could be more land that Quote cannot or doesn't need to get to.
Certainly Pixel didn't finish the maps perfectly, but if you take into account the possible flipping effect due to doors, as well as rotation into a third dimension (depth), most of it is possible (Hell is a bit of an exception, that can't match up with Plantation without an extra not-shown tunnel between the door and where Heavy Press falls.
We don't even know how big the island is itself. For all we know this could all be happening in a very distant corner of the island, or the Sand Zone and Grasstown are way farther away from the Mimiga village than you'd think.