Funny, I had the exact same question, and spent the last hour or so looking into it before I saw your question.

In something I've been writing lately, I've wanted to be able to use certain typefaces, but they lack mathematical symbols or characters. It's something I run into repeatedly. Earlier today, before I saw this post, I was thinking maybe I should just add them, because they're open source, but then when I saw this I wondered "could you just do this with an autoencoder or AN or whatever?" It seems very doable. There are typefaces with them; the issue is creating the missing characters for the typefaces that don't have them, but have other characters.