That's not what I'm talking about. .WMP used to be a text format including documentation. Now it's some proprietary binary format there's no documentation for. It's not so much the fact that the new .WMP files are binary files, but the fact that they're not documented so I can't easily write a reader.

Update
I found the format of a .WMB file instead. I could just use that and the problem of lights is already taken care of.

The thing is, I really, really don't want to write my own Level Editor when I've got one. I want my engine to read as many formats as possible, and it's open source so people can add more formats, mix n' match.

The engine chops off the file extension to every entity if there is one- it loads the required sprites and models using simple names in it's database. For example, every sprite in the level has a copy in the .WIP image packs (which contain sprites, textures, or both in 24 or 32 bit formats).

As a bonus, the engine will work on anything that supports SDL and OpenGL. It will even read the skill values you set in WED and the first to strings and look up the action in the database.

Even if I personally decide not to use it, it would still be nice for other people if it works with .WMB files. I see I can do all the light maps and have a beautiful level, and the material names are all in there as well. It's going to be easier to implement than a text-based format and the documentation says that the format is very strongly backwards compatible.