It does, right? I imagine you would be map syntax highlighting rules and colour themes over to this convention in order to generate a new set of glyphs. I'm sure it isn't trivial but it could likely remove or at least alleviate one of the cons listed in the article.

This is one of the cooler things I've seen in a while!

Definitely! For example, Glyphs has a decent python scripting API which could be used to automate the whole process. I used it for automatically assigning each layer the correct color attribute to save me some clicks. And I also generated all the calt lookup rules from a list of keywords.

I wonder if you can load a font from base64 string like you can with images. Then, one may write a pure js library which generates such font from a set of rules on the fly. Catered to a specific use case.