I fail to see how this is "easier". Even if the router is also NATing, it'll still process packets that don't meet the condition to be NATed, which means that your ISP can send you packets with the dest IP set to one of your LAN machines and those packets will happily be routed onwards unless you dropped them with a firewall. And therein lies your disconnect with those who disagree with you: you understand the networking concepts. A torso. Cost of setting up firewall - I don't know.
nest...