Well i think there is a more simple way. If the player limit in each district was much higher, like 80-100, and threat is not a restriction (you can join any district at any threat level) and then the Matchmaking do the rest by just Matching the players depending on their K/d/ threats etc. This will really reduce the time needed to join district and find a mission, but well, only problem is the amount of cars / player on the same map then.