Yes! It's about time! I was just about to create a map editor for the 4th generation, actually.
Looks to me like it's pretty easier than all other generations. I wish you luck with the editor, because it looks like you'd pretty much be the first to ever have a map editor for the 4th generation.
I'd might as well work on attempting to create a map editor that would edit the hex in the ROM and not have to extract the ROM in order to do so. That is... once I learn how to use Microsoft Visual Basic.
But great work, I'm not sure why no one was doing it earlier. Because this will be... the beginning of 4th Generation hacks. So we're no longer stuck in the past of 2D hacking anymore, we'll finally be able to edit 3D! YAY!
However, I'm not sure if the grass and house are in the same objects. Are they different again? Or is the grass an object?