> Well, NAT saved us from a certain doom, and also provides extra security
NAT is a horrible hack. It might be a good solution for some things, but to fix the addressable space option, it is a disaster.
Talk about an almost entirely useless "broadcast" only Internet. Is that what you want?
> (might act as a firewall).
Even worse. I don't even want to begin to explain to you why you are wrong about this. The broad adoption of UPNP makes the idea that NAT provides you with a useful firewall complete idiocy....
If you want a firewall, make a firewall. Do not rely on NAT. Ever.