YES:
 * Downloading rootfs over http
 * Specifying rootfs location filesystem type
 * Other compression algorithms
 * Start different init than /sbin/init
 * Configuration examples, HOWTOs
 * Rootfs "overlays"/"parts"

MAYBE:
 * Compression algorithm autodetection based on filename OR bsdtar automagic
 * Fancier OK/FAIL - at the end of the line, or somewhere