On the other hand, if you want to play games on your network you absolutely must have UPNP. Unless the game has a dedicated server infrastructure. But even then you risk higher latency on VOIP if it even works at all.
This is completely false. Almost all home networks use port-restricted NAT, which allows for STUN for NAT traversal. You do not need UPnP to play games, even those that have peer to peer multiplayer.
Also STUN for VOIP does not increase latency. It tells you your external IP and port.
I have and I manually manage my firewall. I have never seen a game that only uses/allows one port so IMO it would only become a problem with something like 10+ consoles playing the same game at the same time and all of them being a host. If even then.
This is not a reasonable solution for most people, it requires intimate knowledge of the games you play (which ports they use), a static IP for your console and no more than one player/console per household.
Heaven forbid you have a PC game and a Xbox game that have conflicting ports.
And, I just have to say: you open arbitrary ports to your game console from the internet and talk about security.
If you want to host servers on your network then you need firewall rules, but if you are just a client then the firewalls implicitly allow the responses to client traffic through.
