I know that the .res files, at least for the CAS icons, are 128 x 128 DXT4 images, but since the DDS plugin won't let you save a DXT4, you can save them as DXT5 after changing them, they will work in place of the DXT4 textures. I haven't delved deeper into the actual textures on the body, but I ampretty sure they are more than likely the same format, but of a larger size, more like 256 x 256 or maybe 512 x 512 or something like that. They could be DXT1, but I'm pretty sure that most hair texture is prolly DXT4, since it can have different degrees of Alpha transparency instead of a single bit Alpha, which is what the DXT1 textures have.
Of course you must take the game header off the file, if it has one, the save files do, then supply a good DDS header, edit the file, then take the header back off, and put the game header back on.
The .res files the game uses do not have to be resigned, unless it's a CAS icon in the save folder, and I don't think they do have a header, so those should be easy to edit, as long as we can get an importer into the WAD files. This would allow hacking of characters and other stuff in the actual game, but to actually add any new stuff to a CAS, you will still need to resign the files, which I will have a program soon that will do that.
I haven't had a chance to totally figure out the .k file format, but hopefully Mr. Mouse already has. I just haven't had the time to disect it yet, the other stuff I've done is easy compared to that. I was one of the big pioneers in hacking WWE Raw for PC, and figured alot of file formats out for that game, so I could easily do it for this game if I take the time. My only problem was the WAD files, because I am not good with compressed formats. Once I found out that this program could extract them, I was happy, but sad that we can't import, at least yet.
If you haven't seen my ultra new movie, go to the forum at Xbox Saves or GameFAQs and look for the new links.
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I don't actually play the game, but I can see what you mean. 
