Open up the game for anyone to join. Provide incentives for joiners like bonus keys regardless of how the match ends. same for both hunter and monster sides. Give a 5 sec timeout upon connecting for the player joining to get his bearings on the situation.
Punishing leavers at this stage does not serve the purpose really well. From TRS/2K pov, the bigger issue is to attract and maintain player base. dodgers/leaver do not constitute a large portion from my experience.
Open up the game for anyone to join will help the remaining 4 players to enjoy the game. Usually once the monster focuses on the AI bot and downs it, the rest of the hunters leave.