The contents of the perspective folder (fonts, themes, styles) will be maintained in a gateway backup - it’s just that, on an upgrade, we may replace the defaults (ie,
dark.css) with new versions, because we have to, because we’re constantly adding new components. You can just copy the existing css file, add your custom font rule to the top, and use it as if nothing changed.
While we do have some vague plans to make themes more accessible at some point, but it’s fairly low on the road map. As came up a few times at ICC - our development motto is unofficially “first make it possible, then make it easy”. Right now, custom fonts and theming is possible - but we’re aware that it’s not easy.
As for automatically detecting fonts in styles - that’s just not practical (or, potentially, possible). What may happen is some kind of “font upload” tool that lets you add resources, and then they’ll be automatically kept updated. But, for now, the solution with manually creating themes is the “right” way to do things (and certainly supported, since it’s literally how we’re doing things as well).