It exists as the file /sbin/hijack, which hijack will try to execute in favor of /sbin/init.

Wait wait wait.

What if hijack were changed so that preinit could exist somewhere specific on Drive0 instead? Then one wouldn't have to re-install preinit on each upgrade, and the empeg guys wouldn't have to get involved.

Then if your mountpoint stuff could somehow be worked into a startup script, preinit could be a painless thing. Then all add-ons could go onto Drive0 and nothing would never have to be reinstalled after a .upgrade.