I think Darktide deserves some survival-inspired mode with extraction. This could also be used for getting max LVL characters instead of leveling one.
Raw concept:
The player spawns inside a map that has 2-3 paths that differ in difficulty and enemy types(Most maps have multiple paths used in different missions this idea uses that for unlocking certain path that sets your difficulty).
You start with some grey melee weapon and move your way through map while solving puzzles to overcome obstacles or to get into the armory with better weapons (blue/purple/gold) or to avoid enemies etc. Once you reach extraction you keep what you found and get a character that max lvl.
Alternatively, you could start at level 1 and level up through this playthrough to max level with certain guard posts/ med hubs with the terminal to assign skill points.
You can do this solo or choose public to meet random players as well but the extract will be limited to 1 player.
For seasoned players, there could also be a gamble mode. You get thrown into a map and If you fail to extract you lose your items completely. But on the other hand, you can find some let’s say RED items that will be 550 (like 85 Max stat on weapon) and if you finish all this you get to keep them.
The additional idea is a prison break type of mission that starts after you fail the mission with the public and you have to get out and find your stuff or lose it completely. The same could be done with your character to add to the stakes a bit more.
I feel itemization rework gave a possibility to gamble with your items a bit more since it’s not that big of a loss now since you can somewhat easily get decent weapons any time.