I've recently added a whole bunch of NAT forwarding, but forgot to
remove some of the old Firewall rules from previous ones. When editing
some of the NAT rules, I remembered that it doesn't update the
Firewall rules. Thus, I just set the firewall rules to allow any
incoming packet for now, figuring NAT will work itself out on that
part, and the rest shouldn't effect m0n0wall just yet.

I know I should go and customize the firewall rules again, and I will.
I know that it currently leaves me open to an attack if m0n0wall has
some undiscovered bug in it. But I was wondering if it would be
possible to get a feature to re-add the NAT rule into the firewall
rules, and maybe when editing a NAT rule, to update the firewall rule
with it?

Maybe even a global do-all for NAT rules where you can convert all of
them into firewall rules in one big swoop? This way, for those that
edit NAT a lot, can just delete all the incoming firewall rules that
apply from NAT, and then just do a big global convertion.