I’m thinking about creating a constructor like https://universalsans.com/. Especially about the second part with selecting alternatives:
How do you think, or maybe someone knows exactly, how this customization works on the backend side?
Is it just a preprepared list of fonts that cover all cross-pointed combinations? Or is there a command-line server tool that modifies font files — swaps alternate glyphs, turns on/off features, et cetera?