I've started adding God of Thunder support to Camoto, and I have now been able to successfully edit levels:
Unfortunately I still have to figure out why the game does not like the way I am recompressing files (the maps won't load unless I manually tell the game the maps file is not compressed) so I will have to figure that one out before level editing works out of the box.
But as you can see from the screenshot, there are a number of unused items in the game. When running in debug mode I get errors about missing script files when I collect the items, so it looks like there's a possibility of making them actually do something in the game. When they show up in the inventory they have names like "FUTURE" and "UNUSED", which I thought was interesting!