A good way to do this would be utilizing DD-WRT and an old Linksys WRT54G. use the wireless or the internet port for internet, interior LAN ports for the games, and a VPN config.
The ultimate would be someone host a vpn connection point, and the DD-WRT boxes would all connect to that point. Otherwise, who you are playing with has to drive your configuration change each time.
I've been intending to try something like this, but I don't have internet where my Rush the Rock is currently, nor do I know someone local with another RTR to attempt this with.
I don't know what the effects of latency are on the game, but with modern broadband, the throughput shouldn't be a problem.... but latency may effect game play.
I'll have to check back here later for more comments from those trying this.