Like the summary states. I'd appreciate adding support for systemd eclass as well :P.
This might become a not that easy task. It seems like upstream finally split up the extras (functionality with external dependencies) into smaller pieces: --disable-rule_generator disable persistent network, cdrom support --disable-hwdb disable hardware database support --disable-udev_acl disable local user acl permissions support --disable-gudev disable Gobject libudev support --disable-introspection disable GObject introspection --disable-keymap disable keymap fixup support --enable-floppy enable legacy floppy support --enable-edd enable disk edd support --enable-action_modeswitch enable action modeswitch support Not only do we have to figure out what option en-/disables what dependency on external packages but we also must adjust every ebuild depending on sys-fs/udev[extras] to reflect the new USE flags (given that the "extras" USE flag will be replaced).
Commited udev-171.ebuild with these split use-flags.