I believe it's possible to create a IP lock in a map, let's say for exemple, 192.123.456.2 logged on the map, then no other 192.123.456.2 would be permitted log on that map as long as the other one still remains, but then again this may be an issue for the Internet Cafe users which would be a minority in most cases, but that is, to what point are we really wanting this event to be a success, are people even willing to sophisticate such a script for the likes of an event? But then again, same script could be enforced in GvG and LMS