Hey thanks brothers for thinking of us people down here in Australia!!!
A region filter would be great in addition to the ping. I believe Call of Duty: World at War was one of the first games to feature a region filter. I can tell you, it was VERY well received by Aussie xbox forum members. (not sure if PS3 also had this feature?)
However, if it is something that would delay the release of the game, please don't worry about it! I want to play the single player game as soon as possible.
Usually i only play on xbl with my friends, but i will be happy to swap gamer tags with you guys once the game is released!!!