Allow people in the same chat channel to start a party. This party has a leader, and up to 4 more players in that party. People can be invited to the party by the leader only. When the leader joins a game, he brings his entire party into the game with him. If there are not enough slots in the pre-game lobby, then he gets the message "Server Full". This would do two things.
A) It would allow parties to join games quicker and in a more organized fashion
B) You would be able to see how many members are together at once