@boozel
Here is my interfaces for using wan plus a separate bridge. They all come up for me on boot.
auto lo
iface lo inet loopback
auto eth0
iface eth0 inet manual
auto wan
iface wan inet dhcp
auto lan0
iface eth0 inet manual
auto lan1
iface eth0 inet manual
#
auto br0
iface br0 inet manual
bridge_ports lan0 lan1
bridge_stp off
bridge_fd 0
pre-up /sbin/ifconfig lan0 up
pre-up /sbin/ifconfig lan1 up
Hope this helps.