You need six players just to start a private match with friends and that's a lot if you ask me. I believe there should be no minimum limit. Some people may want to try their custom map with 2 or 3 friends. Also, there should be an option for 4 player co-op mode and not just 2. It would make the game way more fun in my opinion to have more friends playing in the open world. But that's not as important as private matches with friends. Trust me a good multi-player game will always bring more players to the franchise. Please make this happen with the next update.