I think any enterprise that fails in this way has way bigger issues, and I would expect to have already been compromised. Every single enterprise should already

I think any enterprise that fails in this way has way bigger issues, and I would expect to have already been compromised. Every single enterprise should already have the firewall rules on their edge routers that would prevent that set up even with IPv4 (remember, NAT is not intended as a security feature and only kind-of works like one. Any competent network engineer should not be relying on NAT to add any security).