20 years ago, russian programmers managed to squeeze the Cyrillic alphabet into PCX files ... the text turned out to be not very beautiful, but you can read it…
IMHO, you can only change PCX files from NOLF2.REZ \ INTERFACE \ FONTS
In the future, you will add your Polish CRES.dll to the converted PCX files and format it as a REZ file. Other files cannot be modified (IMHO), as there will be no compatibility with different versions of NOLF.
By the way, maybe you have CRES.dll Polish localization of the game "Contract J.A.C.K."?
I now have these GUIs for Contract J.A.C.K. : English, German, French, Russian. It is interesting to make the Multilingual Patch for Contract J.A.C.K as well!