Thanks. As you know, I got the idea to make a WL2 editor after seeing your editor. Here's the new release (version 1.2.0). Right now, only some of the graphics can be edited.https://app.box.com/s/zmgumc6u7dxujr41dr2r2vrho4b4o2n5
The cutscenes are a bit annoying to deal with because of the address shifting with the graphics. Most of the cutscenes actually use their own graphics, but some of the graphics from tiles and objects are used in the cutscenes. Hardcoding the addresses that point to the graphics would probably be the best approach for now.
For graphics editing, I may plan to expand the amount of tile graphics that can be used in the game. Since the pointers to tile graphics use 3 bytes, it's possible to store the graphics anywhere in the rom. I'll also try to expand the amount of metatile, tile color, and tile type sets that can be added in the game. There would have to be a lot of shifting around of data in the rom for that to happen, though.
Also, out of curiosity, what was your approach to hacking the rom? I basically wrote a custom hex editor, then primarily used that to corrupt sections of the rom. Then I uncorrupted half of the corrupted section until I narrowed down which part did what. I never tried to understand the assembly code of the game, though, so I have no idea how the code of the game executes.