From my experience as a gamer and not game developer . what a game engine can do is to add support for text to speech TTS for menus , popup messages and in game dialog. This engines will allow you to enable TTS support, and would make it easy for users to change the font sizes for example. I am not sure if there is a cross platform TTS interface.

My initial point was that if you want to make a game and not some hobby project try using existing engines, I have nothing against hobby projects I am also considering experimenting with a game that would simulate a world using Prolog , but this would be a toy/experiment.