I suppose you or anyone else may begin with simply modeling-unwrapping-texturing something and just showing your work up. With a 3D Ripper you can investigate how many polygons are wasted on trees, cars, household items, etc. Textures resolutions. For example any could make a hunting double-barreled rifle and, perhaps, if done nicely, it might be just included in the game. Double-barreled rifle do needs additional animations, which is tricky without having an access to modified Dark Unity, so anyone may start with something static like new sofa, watertower for a village, etc. I suppose it is not restricted to create a whole new tiny location like Raven. All in all I just want to say that it is always better to make something and show up, than to ask a permission. You just have to stick to the visual style of the Long Dark and consider how exactly developers spend polygons on their props/assets. And, of course, that's my own opinion, no insulting, maybe I am wrong.