Allow updating fonts to current formats
This is going a bit out on a limb, but akin to #13 in the "management tasks other than installing/uninstalling" category, it might be useful to enable users to automatically convert a font file that they have in an archaic, unsupported format into a supported, contemporary format that they can use on their system.
The main examples here are someone who has a PostScript Type-1 font which could be converted to a CFF OpenType font, and someone who has a BDF bitmap font which could be converted to a OTB OpenType font.
Although there are near endless possibilities for how any given format conversion could be done, full-blown font editors and build chains already cover those; a handful of simple/naïve converters would probably cover 90% of cases.
To be sure, such conversions are not the ideal path forward, but I'm sure everyone who has paid attention to the various text-related GNOME projects has seen how often these archival font formats seem to spawn irate arguments. I suppose to a certain degree those incidents seem like there's a disconnect between the user's understanding of the shapes they see on-screen and their understanding of the file formats — e.g., 'the letter shapes are still there, why can't I use them like I used to?'.
In a perfect world, somebody would help those people understand the structure of the file formats and help them find an equivalent modern font, but it might squelch a lot of vehement debates to just be able to point at a button or menu entry, and let the user go (or drop it) from there.