Thanks Chris.
Yep, I've seen that menu many times while attempting wan/lan/nic combinations.
Woke up after a few hours, tried it again, it works. I have no idea what the problem was but I know I was impatient last night, plugging and unplugging interfaces during the boot to get around the watchdog who seemed annoyed at only one live interface. (my LAN consisted of a laptop with a low battery, and it kept sleeping)
From what I can see so far, this is a VERY nice solution! Kudos to everyone involved.