Suggestion from Winterwolf#6210 (213528659372277760)
So this might be a bit harder to implement with bots... but the bots suck anyway and most people just try to squad up. Like seriously, sometimes these guys don't even shoot during swarms. Anyhow, that's not the idea.
The idea is a level that has several parts where it forces the players to split up. Effectively putting levers or switches in rooms that need to be activated simultaneously in different rooms. And hell make it where you have to progress carefully in this split.
Think of it like a series of interconnecting tubes, where your only way forward is when the other player(s) in the other tubes hit their checkpoints. The cost of both players going down... is Neurotoxins being released into the chamber containing the other two players, putting individual player skill to the test.
Here's a really lame visual.
Starting Area] Splits off into two tunnels = = = [Checkpoint area] splits again = = = [Checkpoint area] = = = [End
The split routes could be very diverse and lengthy and having their own separate dangers. For example one winding tunnel could have lots of Infectious fog present, while another might be crawling with Big Boys (The tall sleepers)
I suggest this to add another element of horror to a mission. One of the keystones of horror is that people are brave in groups, by adding in a mechanic in a level that splits up the group, it adds more to the horror Factor.
Another element is powerlessness can create that feeling of horror as well. Knowing that your life might not entirely be in your own hands is kinda terrifying, its in another player's hands, and likewise theirs is in yours.
This is a double whammy of horror! Now I'd only recommend it for a mission or even just a part of a mission, but I think it could be fun! Especially if someone alerts a horde and both teams of two have to fight at a disadvantage!