I’ve finally finished setting up a FreeNAS box as a local Debian repository mirror. I’ve done this with a new feature of FreeNAS - the web server! The document root holds debian/ and I’ve set a cron job to rsync with a local repository every night at 3AM.
I also updated my local DNS resolver to use that FreeNAS box IP address as the host IP for ftp.debian.org and ftp.us.debian.org. So far I have not experienced any major problems. :-)