Trying to undub FFX (PS2)

[Toastbrot]

Hello everyone!
I know that there's already a FFX undub but I wanted to make one with the German subtitles instead of the English ones.
Reason is, the German translation is more faithful to the original script than the English one.
Unfortunately, I have never done anything of this sort so I'm kinda stumped on how to get the necessary files.

I've dumped my German version and got my hands on the undubbed ISO and extracted both.
They're the same files (even the same hashes!) except for the ELF and SYSTEM.CNF (which is just an ASCII text file).
Meaning, the necessary changes have to be done in the ELF itself, doesn't it?
The ISO is full of *.IRX files which are, after doing a little bit of research, like drivers to the PS2.

I've been trying to get more information about this but it's either that I don't know how to search correctly for the necessary information or that there just isn't a lot of data floating around any more.

Spoiler: ISO contents

ATAD.IRX
DEV9.IRX
HDD.IRX
IOPRP234.IMG
IOPSOUND.IRX
LIBSD.IRX
MCMAN.IRX
MCSERV.IRX
PADMAN.IRX
PFS.IRX
SCES_504.92 (Ger) / SLPS_250.88 (Jap)
SIO2MAN.IRX
SYSTEM.CNF

 

[undubfan]

Did you made any progress? Or maybe succeed if I may ask?