As far as I know, you cannot do a TCP NAT punch through; it is the prevalence of NAT in the consumer space that was the real reason to drop use of TCP for consumer hosted games.You ever have tried to establish a 8 player RTS session with random people, even when using a master-server ? Ever have tried to establish a tcp NAT punch through ?
If you have a lobby server or master-server list in the clear, it can do NAT tunneling for you, so there is no need for someone to have a firewall setup correctly.
And RTS games are the classic example of games that are run on a Peer-to-Peer architecture rather than client/server model, in part because of the ability for a player to be defeated early in a long running game.
What exactly are you trying to do?