Thanks for your response FF7Remastered but I want this little patch to be able to work for the re-release edition too and the easiest way to install (by only replacing the menu_fr.lgp file). I already spent a lot of time understanding the *.tex file's header, everything's working just fine except for all the outside battle window textures...
It's curious that all the rest of the textures works perfectly so I'm clueless how to fix it.
Here's another example: the countdown numbers are supposed to be the same ones as the HP and MP numbers (numbers are upscaled and works great in the battle window but not outside of it, they're keeping their original size and position of the original *.tex file).