I really wish that more games had been made like Battlefront.... It's nice haveing complete control over the game server...
The only way that you might be able to do something like this is get ahold of the actual software for the servers.... and then everyone in your "group" would have to use routing to reroute the PS2 packets to another IP (the one of the server you set up)... because the IP's for the servers are either stored on the DNAS server or written on the Disc.... the DNAS servers are on the disc...
With lots of work you might be able to snoop and log all the packets to and from the PS2 and try to write a program to emulate a server... but I imagine that each game has it's own server program
PS3 Slim 320GB
PS2 v11 exploit w/300GB Maxtor
PS2 v10 exploit w/80GB Samsung - Network Games
PS2 v10 exploit w/60GB Samsung - Network Games
PSP 1001 3.52M33 w/10GB total storage
NDS DSReal 4GB