Oh, no wonder I could not make sense of those files in any encoding I tried! To uncompress them I should use the original bms script, right?
Something else: my listfile differs from your last rootR_mixed in the sizes of Sys/en/SysString.bin and Sys/ja/SysString.bin. Yours says 868 and 3213, respectively, while mine says 17011 and 11433. My values come from the files I copied from the US version's USRDIR\Sys to my us_files folder.
The sizes of my SysString.bin files upacked from the japanese version of the game (688 and 2124) are also different from those in your rootR_mixed, so I don't know where you got yours. Can you think of anything I may be missing?