Creating diff was also in my mind, but there is no bnk repacker so you can't hope to use WemTool on the inside .wem files, since there would be no way to rebuild them.
If there was a bnkrepacker, we might have saved 150~200 MB (only 1~2 MB compression with WemTool on 80 MB files)
BKHD header occurs at different places in different files, i think there is no pattern + we can ignore some 1 KB ~ 1 MB files
