But notice that private networking is more complex. If you want to reach non-public server, either you have to log in into a public server in the same network and then open another connection, or you need VRF routing (ouch!).

With IPv6 you can just ssh into the box directly.

That's a lot of surface area you're exposing.

Yeah, this unfettered inter-networking sounds like a really bad idea. If only there was a way to control access besides fragmented addressing islands...

Some people put public v4 addresses on machines already. I would if they weren't so scarce.

That's what firewalls and packet filters are for.