I've been trying to make co-op/single player maps for my episode -- it's very hard, a completely different skill set than deathmatch/duel/CTF. I've been adjusting the monsters to be more interesting (and less like duplicates of Doom monsters)
Stridicus -- fires out a stream of five, weak, homing slime balls that do not follow you very well, there is a 50% chance that they will lose you as a target
Gyro -- very fast, very agile, very light, and very hard to hit, with low health and a weak attack. An interesting enemy. Not dangerous by themselves but in a group they can be dangerous.
Cycloptis -- Lighter, faster, and with more health than Doom's demon, though you can "push" through them now if you hold down the fire button with the rapid zorcher
Flem mine -- Currently it floats around gently until it sees you, then it charges at you tightly following you and detonates on impact, though I've found that this behavior is more suicidal to the flem mine than dangerous to the player, they generally only explode on walls. I don't like how this enemy works, but I don't like it as a lost soul either, suggestions?
Quadrumpusguy has made a few new enemies as well
Unfortunately it will be a while before I can have a full episode of maps that I can release. I'll make it eventually, though, I'm sure of it.
While I've been struggling with single player/co-op mapping, Quadrumpusguy has been doing better than I've been, I've imported most of his work into the main pk3, though some of his levels are missing, he hasn't finished some of them but the maps I have played are very impressive. They will definitely be a part of Chex ST Pack P17, though a release date on that is unknown.
I've also been working on a side project which turns every Doom 2 map into a CTF map. It's not Chex Quest related, but it's something to do when I get tired of trying to map co-op maps. I have done maps MAP01-MAP08, Quadrumpusguy has done MAP14.
@Flem Mine: Maybe they should be able to explode several times, say 3 or 4 times, which would make them more dangerous