The sellable items should make a return personally. And, maybe have some function? Stuff like the documents could be used to give some lore tidbits that the company wishes to keep hidden from any one, and out of curiosity you can just have little peaks in, and find more stuff out about the world, maybe even outside the anomaly that they aren't telling you.
Voice recorders could be an amazing way to tell a story of another explorer or maybe even another group in the anomaly, or maybe some music like some of the tapes before? It makes sense that the player's equipment is upgraded due to the years, but the tapes and what not could still remain the same really, maybe be able to by a portable radio from the shop for the music tapes? (And please keep them physical so you can eject them too, i hated the fact they disappeared when done and could ONLY be accessed via the pc :<)
Other sellable items would just be nice to have back. But would probably warrant another backpack tier due to how much stuff you'd gather at that point.