The inventory feels a little small, especially because more or less the first row is "dedicated" to stuff like food, drink, ammo, meds,...that I guess noone leaves home without.
Just making it have more slots (like many mods do) can make it somewhat tedious to organize it, because it gets cluttered up fast.
Following idea might work to have a bigger inventory whilst being able to keep things organized:
Keep standard size of the backpack as is, but add "mod slots" to it, that add specialized compartments that can only contain stuff that fit into a certain "category" like meds, ammo,...
These compartments could maybe hold up to 2...4 items only, and would be arranged around the main inventory (more or less same as with real backpack addition pockets)
So if you find such a compartment mod, you get the additional slots, but can only put in stuff that fit into the corresponding "special category".
Therefore you gain some "common space" in the main compartment time after time when you find more of them.
"special compartment mods" could be for example:
-tool compartment (up to 3 mining/harvesting tools, like pickaxe, ratchet,...)
-ammo compartment (up to 4 full stacks of ammo)
-med compartment (up to 3 medical supplies like splints, 1st aid kits,...)
-fluid container compartment (up to 3 stacks of different beverage)
Each additional compartment could make you a lil bit slower, or chew into your stamina usage, just to add some downsides.
There could even be a book series about the backpack, e.g. for unlocking the crafting of the compartments (e.g. fluid container could use cooling mesh and insulation mods),
compartments don't slow you down so much, add one more slot to them, and so on...
Thank you for your thoughts on this.