I was going to do a custom format with zlib compression, due to the amount of tiles it spews out..any code in your current version that rely's heavily on the format you're using now?
The object layer probably is the biggy as the content of the tile will change therefore the lightmapping wants to avoid this layer. And of course the collision, but I guess this is all fixable!The door code looks at if you're colliding against a door object and if you are checks if you've got a key, if you do it removes object and collision data from the map file to allow you to pass.
Check out the new code and see what you think.