Yeah there is no directory beyond data, only the BSA files, and no program I can find lets me edit them, I simply created a textures file and that didn't work, I modded oblivion easily enough but have to say skyrim has the better of me.
How did you unpack/pack the bsa files? I'm trying to add some mod textures to the game but cant for the life of me figure it out its driving me f***ing mad!