Make an easy way to switch to spectator mode from within a server game.
To stop people abusing this ability, we probably also need to implement a cool-down period to prevent rejoining, and/or a ´tournament’ flag on a game that prevents new people joining mid-game. Alternatively, when players leave the game could keep details like team, respawn time, and upgrades on file for if they rejoin during the same game—this might be nice for cases where the connection is lost and then re-established.