I have an idea, but it would probably suck to program in. When people first join a server they can check out if it is a good one (spawn in as a goat in a random place and have a 1 minute limit to prevent goat spies). Then, if the server is good, the player can decide to join the game as their character. Once joining, the person would be unable to join a different server for 30min or 1hour(unless the server goes down).