Comment 5 for bug 42926

About the Bitstream family being the default:
I'd much rather see DejaVu LGC Sans as the default. It's a Bitstream derivative with added Latin characters (covering many minority languages), added Cyrillic and Greek. It also aims at keeping the same quality as Bitsream Vera fonts, i.e. hinting, kerning and other basic or advanced features.

We recently added Arabic Script to DejaVu Sans, but since it is unhinted and inappropriate for some users, DejaVu LGC Sans is more suited to be a default font.

see Bug #40553 for DejaVu LGC Sans

20 is not enough for all the Scripts currently supported by default, but could be done if more fonts are installed through language support instead of by default.
I don't think that many users care about all those Scripts, I'm sure there's a better way to make sure these fonts are installed for the users that care.