I suggest font_fc_config function for install fontconfig config file. It works with >=fontconfig-2.4.
Created attachment 100021 [details, diff] font.eclass-fontconfig.patch
Created attachment 100022 [details] media-fonts/vlgothic/files/64-vlgothic.conf (sample)
seems reasonable. But is it a good idea to enable all config files by default ?
I implemented this and then found this bug report. ;) The new variable is FONT_CONF, and is a space-delimited of fontconfig files that will be installed into /etc/fonts/conf.avail. Symlinking them to conf.d is up to the ebuild or (preferably) user.