If you can put the possibility to change the font size gui.text_size is more than enough, the problem with the font size is only in the dialogues, I always fix the menu interface myself. If it is not possible it does not matter, I modify the gui.text_size or screen say() in my zzzStartGB.rpy.
If you can provide me with the list of modified dialogues (old->new) it is very welcome. The fact is that I play it personally, so I manually fix the translation of those sentences that DeepL translates badly, but the dialogues already read if they are modified I will not see them unless I start over.
Anyway do what you can, I do not want to distract you from your main work.
Thank you very much.