questions of MP construction

[R'as al Ghul]

Can you disable the firewall of your router and forward all ports?
That way the IP's of the machines behind the router should be visible on the net with different IPs.
I'd recommend to use a personal firewall on each machine, like Sygate, and allow the game to access the network.
CA has written MTW in a way that fakeservers, like for STW, are impossible or very hard to set up.
The gameserver adress of gamespy seems to be hardcoded and is not read from a txt file, although such a txt file exists. They didn't want people being able to use fakeservers, like the Shogun one.
If gamespy turns off the server in the future the only way to play will be Hamachi.
Which, by the way, could be a solution to what you're planning, because it sets up a VPN and tunnels through everything. You can read it up on the net.

R'as