That's exactly what I did and game just closes when I try to login with my account ingame, I opened l2.ini with l2encdec and changed server adress but it doesn't work.
I think its just protected, but what a retarded protection if I can login with OOG.. I would use OOG but is a pain in the ass.
edit: I tried to login with the l2.exe in the edited l2.ini system without using l2net and same happens, the game closes, I thing that the server protection detects if the l2.ini has been modified?