Multiple, mostly item-related suggestions
A lot of these have probably already been said, so I'll just dump as many here as possible.
-Ability to use tarp to catch rain water, which is always clean except for maybe a certain area having contaminated/acid rain?
-Maybe an electronic water purifying "Wand", that uses electrical charge instead of a pill?
-Maybe water filters that are very rare, highly valued, but degrade over time? Would also allow a way to drink chemically contaminated water, maybe depending on grade of filter (Lower grade filter only removes bacteria, high grade one removes bacteria and chemical contamination).
-Armor would definitely be a cool addition, maybe starting from leather armor and going up to the combat armor that DMC guards wear.
-Definitely some more weapons, things like maces or spiked clubs/bats, maybe some unarmed weapons like spiked/brass knuckles. (And a boxing glove, what is manlier than beating your enemy to death with something made to make punches less dangerous?)
-More shelters than just the tarp lean-to. A wooden lean-to that can't be moved and can be set alight if a fire is nearby. Some actual tents would be cool, no point in making more than one since you only need one-person capacity.
-I saw someone post about how it would be cool to have high-tech or powerful things for a player to work towards (Was an apartment in the DMC that this person was talking about). Maybe something similar to the stillsuits from Dune (It basically recollects water that you either sweat out or that comes out as waste, making you need VERY little extra water in the desert) or power armor (Every game with an apocalyptic event and future tech needs power armor). Both would be VERY expensive to fit with the theme of them being things you have to work towards, power armor especially. Power armor would be more combat-focused while the stillsuit would be more survival focused. If power armor is too...powerful, than maybe just an exoskeleton, with or without armor.
-As an extension of the thing above, maybe less powerful mid-tier things that give advantages to various skills? Ghillie suit for hiding, a targeting assistance implant (Basically an eye implant that points out vitals, like a less advanced smartlink from Shadowrun) for ranged and melee combat, stuff like that.
-Electric chainsaw as a weapon, nuff' said.
I'd say that's about it, I would go on more but I really had to think a lot for some of these ideas and I want to go back to my videos.