As code space is not as cramped as it was in the good old AVR days, we could add more characters. Also, although there is 3 fonts, we currently only use one, and I don't really see much need for the two others, so they could be dropped in exchange for more characters in the "main" font.
Fonts could also be loaded from the card, but that would consume RAM, which we want to save for games and plugins. Also, there would still need to be a default (but minimal) font.