Short answer: might be a lot of work
The fonts are encoded as images in the "zei" files, including most characters from the
Windows-1252 set (see my screenshot).
And what are .zei files? I was able to load another language in the game by adding a bunch of those like HelpNormal.zei, MainMedium.zei and so on.
How so? IIRC translations are stored in Texte.dat (which is a plain text file).