One of the most compelling inventory management systems I've seen comes in the computer game
Darkest Dungeon - for those unfamiliar it's a cosmic horror dungeon crawling game where the player manages a roster of heroes, choosing 4 each week to traverse procedurally generated dungeons to recover loot which they need to upgrade their home base, unlocking upgrades for the heroes which are then needed to challenge more difficult dungeons until they are ready to face the eponymous Darkest Dungeon itself. They begin each traversal by purchasing supplies and end each with (hopefully!) bags full of loot. It's a model we can recognise in structure if not detail from a fairly stereotypical D&D-like RPG.
The inventory system has a few major factors
- Slot based - every item stacks to a different amount (so food stacks to 12 units, torches to 8, firewood for camping to 1, loot gems to 5, "permanent magic items" (trinkets) to 1 and so on) and is unique in a slot
- Limited slots - you have 16 total slots to hold both provisions and loot
- Any inventory item discarded is lost
- Any loot obtained must be picked up before moving on from an encounter is lost (there's a slight exception to this with camping, but it's quite minor)
- All provisions have defined and useful mechanical effects
- Running out of provisions leaves the party very vulnerable
- Provisions are (fairly) expensive and cannot be stockpiled between runs - any left at the end are sold at a fraction of their cost
- Obtaining more provision in a dungeon is possible but unreliable - plus it often relies on additional provision usage (medicinal herbs to make safe tainted food, for example)
- Possibly most importantly, It is not possible to significantly escape the confines of the system (there's a couple of minor things that allow you to increase the stack sizes, but that's it) No bags of holding, no hirelings carrying loot, no mules or carts.
These together are largely utterly unrealistic - purely gamist constructs. Why shouldn't I be able to put a ruby and emerald in the same pocket? Why can't I hang on to my unused torches and shovels? Why can't I leave caches of supplies or loot behind and pick them up later (we might posit wandering monsters clearing them up, the game has them, but it happens immediately with no chance of failure)?
Taken together however, they produce an experience that I think evokes the thoughts and behaviours that we'd like to experience with an inventory system
- Preparation is important - too few supplies is dangerous, too many is wasteful. The right mix of supplies is also of critical importance.
- Rationing of supplies is important - it's often possible to obtain extra loot by non-critical use of a provision but doing so may lead to danger later when the provision is needed. Conversely, not taking advantage of opportunities risks the provision being wasted
- Choosing what loot to take and what to leave is important - because of the stacking rules picking up a ruby might prevent you from picking up a jade, but if you never find another ruby and find several jades, you'll have missed out on an opportunity for more value
- Choosing when to discard provisions in favour of loot is a continual battle - there's typically more loot in a dungeon than you can carry out, but if you wait until your provisions run out naturally then you risk leaving behind valuable or rare pieces that you might not find again.
- You are incentivised to use provisions - any left over are lost so there's no hanging onto a potion forever for "just the right time"
Overall, this results in an experience where the player can learn and exhibit skill at play and where they are continually faced with weighty and fairly difficult choices. It also invokes what we might feel is a fairly "realistic" set of pressures - our heroes, in a treacherous and deadly environment scrabbling for what resources they can, leaving dead weight behind for the valuables they seek.
To bring it to the topic of the actual thread, it's worth noting that weapon degradation and ammunition tracking are not part of this at all, but in theory could be.
The question is therefore - could we develop an inventory system that's of fairly low overhead at the table (so the cost of using it is fairly low) that produces the same kind of compelling questions for the player and evokes the similar "realistic" concerns for the characters?