A really hacky (and quite possibly moronic) way to go about this is:
Find a font you like and throw it in the /game subfolder. Then edit the attached file and change "Roman SD.ttf" to the filename of the font you want. Then put it in the /game subfolder as well.
This will change all the dialogue to the font you want.
Quirky, maybe, but effective.
![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
The game requires specific typefaces. It was enough to use the file font.py from your advice and choose your own fonts changing their names to those from the game (the required names are BRLNSB.ttf, bedel.otf and hermes.ttf where the first 2 can be replaced with any font using the original name, the rest of the fonts from the game are : arial, segoepr, segoeprb, seguisb, trebuc, trebucbd, trebucbi, trebucit) then you can delete the font.rpa file