to have both abilities, bridge opt1 with LAN like you did originally, and then create a firewall rule to permit traffic through the opt1 interface. Default is to block all traffic (i.e: no rules set)
For my setup, I just created a new rule and permitted all traffic through it. Works a charm.
I tryed it and my opt1 still can't connect to the internet, but it can connect to the LAN Pc's.
opt1 can't ping or login the m0n0wall, but it can ping anything els on the network.
Tho opt1 is a WiFi card running in "hostap" mode. Do you think i need to change it to "IBSS" or "BSS" mode?