https://mods.cityofheroes.dev/texturetools/TextureTools.zip
Finally 5 months later... I'm releasing the first version of "CoH Texture Tools", see I'm great with naming stuff... *cough*
With this you can convert from .texture -> .dds (or .jpg for loading screens), This will dump a .json file with the "header" of the .texture file allowing you to re-texture the modified file, you can do an entire folder or single file.
You can, of course do the reverse, take a .dds (and .json) and re-texture-ize it.
The "Converter" Tab, allows you to convert .dds files to png, (From DDS), or from (most) image formats into .dds! Currently it supports either DXT5, or No compression which should take care of most textures. for UI (Icons, maps, or other User Interface stuff) use "None", for everything else try DXT5. Make sure to not enable MipMaps for UI textures.