Re: @Len - That's pretty easy
Also security was an add-on fudge. The original idea of direct use of MAC address to automagically create an IP6 was a total privacy fail. At least they fixed that.
Setting up a firewall so none of your LAN resources or addresses are exposed seems complicated. Maybe it isn't, but the goal of EVERYTHING having a public IP address, just because you can was plain wrong. A dream for big exploitive companies, governments and criminals.