@julian What do you think about an idea to extend .json configuration for plugins, to have something related to external scripts (scripts.external = [])?
Also will minifier use external js? So every reboot of forum will give latest version to the user.
Not really... it's not a common request, and I think it is still best to change it from the theme itself...
Or you can remove the font declarations altogether, from the theme, and then add them in via the Custom HTML form...