I wrote an open-source mod called Controlled Difficulty:
http://steamcommunity.com/sharedfiles/filedetails/?id=738484519 /
https://github.com/notblackout/kf2-controlled-difficulty/
This is typically used to make the game harder than stock HOE, by increasing the max monsters, quickening the spawn rate (removing the game conductor), and setting a sort of script of monster spawns, called a SpawnCycle, that disproportionately emphasizes big zeds. It can also be used to make the game easier -- just as you can set the MaxMonsters to 64, you can also set it to 1.
I've had several users ask me to submit it for whitelisting. I don't know how to do that, so I'm posting here.
If it were accepted, would whitelisting require reexamination for every release?
I've also heard, informally, that I might have to try to modify CD so that it only makes the game "harder", not "easier", (for some definition of those words) if it were to be whitelisted. I've thought about that quite a bit, and I'm convinced it is futile. Even if I did it, it would merely play into the hands of guys running perk trainer maps. And the overarching theme of my mod is giving control to players... I really don't want to take away the "bottom" end of difficulty settings provided by CD just to get it whitelisted, artifically constraining player choice.
I think most of my players who want whitelisting really just want it for personal best updates. If you are uneasy about whitelisting CD due to difficulty concerns and XP farming (even though I think that's not valid as long as perk trainer maps exist), I suspect almost everyone would still be happy with a version of CD that disables XP gain but still allows personal best updates.