New box idea: if you open this box, dead players will be able to play as special infecteds. They can't be stronger variants (red and purple) to avoid them being too powerful. They would get only 1-2 points for incapicating and killing players. If needed, they could have the normal health and speed as in vanilla game, but have the damage and mechanics (infinite smoker tongue range) of the special infecteds here, making them only glass cannons. If dead players are rescued or defibed, they would lose the control of the infected and spawn at the location they would spawn, having their SI either replaced by a bot or disappear. They would drop either no loot or just 1 loot that can't be a weapon. I think this box could easily give a new and fun spin to the usual gameplay and make waiting to be respawned or defibed alot less frustrating. It could be also a fun way for some players to live out their frustration when it's active I assume atleast that it's possible despite the gamemode, considering you can play as a tank the very same way as you can on versus.
This has been tested for a very long time. Strongly upsets the balance (guaranteed loss). And there are many nuances when activating this feature in co-op mode. Therefore, only the human tank is left