Normal gungame, go to the mode, and start with a gun ending with a knife.
Hide and seek
Go to the mode and randomly select the person who will search. Others turn into random items on the map, if you are found, you also start looking for other players.
There are no saves, food and weapons are not enough, ammo is very important, zombies and npc become even stronger. At night, the zombies become almost unkillable. If you are dead, you start a new game.
I think only your third suggestion would be good for being included in the game. It could likely be done by adjusting the config and setting that as another difficulty option. The first two ideas would be better for someone else to mod in since they aren’t relevant to vanilla gameplay in any way.
Sounds like an old TF2 community server, this is possible in U3 but is annoying to setup and play.
Basically prop hunt, sounds like an old server on most source games. iirc modding will have far more capabilities in U4, so you could probably make this on a server if you really wanted to. Kind of adds more variety to servers imo.
II is supposed to be more survival focused. I really don’t see Nelson investing time into “fun” modes right of the bat. I would like to see the possibility of modding those in tho. After all this isn’t GMod.