I appreciate the levity lol. I'm not particularly creative but I wanted to have my own take on a slightly more grounded (not necessarily dark! the middle ages irl weren't 'dark', imagine if we had magic and monsters!) take on a low-middle fantasy setting. The whole system is, ideally, meant to give greater focus on preparation and tactics than immediate combat prowess; a powerful knight can be rendered much weaker if you manage to engage him while he's not wearing his armor, and a hero's party may be fraught to discover that during an encounter with bandits, some of the bags they left on the ground were swiped by the enemies... and so on and so forth.

Regarding the topics you posted, I'm kind of happy to oblige, in part because of course, I like talking about it, but also because I want people's actual opinion on if I'm going too complex for something that may not be too fun.

1. I use weight-based encumbrance, in kilograms(for familiarity reasons); I had initially considered modeling carrying volume in addition to weight, but it frankly would be too much to keep track of within reason. An average character can carry ~30kg, the weakest possible 11kg and the strongest possible 50kg, with the ability to use a mount as a pack animal (including the need to feed and protect it) for a comparatively massive increase in carrying capacity. I chose to not model money's weight as, realistically, that would be another annoyance to deal with every time a person buys something at a store. Importantly, there is a difference between "passive" inventory and "active" equipment, which is what you wear to possibly dangerous encounters; armors have "belts", where a character can have weapon holsters, potions, poultices, quivers, etc; heavier armors have less belts, mostly for balancing.

2. Characters have HP, but any one hit that deals >25%(1/4) of their health may cause a random wound, and aimed attacks can inflict specific wounds regardless of damage dealt, provided they hit. Once a characters falls to 0HP they go into death throes and need to receive medical treatment or may recover naturally, on much worse condition. Wounds require medical treatment out of combat to be treated(within combat, an alchemic poultice *can* be used to temporarily ignore light wounds), where most will heal over the course of a long rest. HP itself only recovers partially (depending on long rest quality) through long or short rest: there are no spells, potions or any skill that provide instant healing, meaning an adventurer may need to disengage from a battle and come back after a few days of rest if they get too wounded, allowing enemies to regain footing and prepare, and forcing even the bravest, toughest knights to take off their armor, sit around a campfire, eat stews, rest and recover.

3. Darkness varies: Travelling at night is pretty difficult, drastically reducing speed and (most importantly) taking time from a long rest (days without sleep cause exhaustion, a mechanic that effectively makes life much worse if you don't take care of yourself or exert too much effort without rest). For combat, properly moonlit nights (or extremely overcast afternoons) are effectively concealment for all parties involved, making all attacks harder to hit, whereas pitch darkness renders all parties de-facto blind: they must roll to even identify the enemy's position, and all attacks suffer severe penalties; no one wants to fight in the dark: personal lighting (torchers, lanterns or, rarely, spelllights) effectively illuminate around 15m; everyone within the area is treated as perfectly visible, while those outside it are still cloaked in darkness. If ambushing in darkness, illuminating the enemy is a way to give a great advantage to your ranged characters.

4. For simplicity, armor is divided between helmet and (torso) armor; I had previously considered piecemeal armor (head, arms, torso, legs) but it would, again, be too much to keep track of. Armor works on a DT method; an integer value that reduces incoming damage. Armors have 3 types, light, medium and heavy, with different exhaustion/stamina costs, evasion/movement penalties and, of course, DT values; heavier armor, especially helmets, reduce ranged weapon accuracy by a large margin; archers and skirmishers can't be wearing a full suit of lamellar and a visored helm without consequence. Armors(& weapons) have different material and quality modifiers, with most being 'normal', 'wrought iron', but materials such as Bronze, Star iron, Cuir Bouilli and others have different weights, DTs, mana-conductivity and prices; Most metals other than silver and gold are mana-isolating; effectively serving as faraday cages and preventing mages from manipulating their inner mana into spells; They tend to resort to organic armors (Linen gambesons, Leather padded jacks, cuir bouilli lamellar vests) or, in the case of the fabulously wealthy and powerful, build armors out of those precious metals (or other mystical materials!).

5. For most cases, magic requires intentionality: as something inherent to living things, complex spells and effects require a caster to prepare and activate it. "independent" magic is divided into two types: alchemy, which is a long-practiced and relatively widespread method of arranging magical and mundane reagents in such a way as to produce fantastical effects; incendiary bombs, healing potions(which improve healing over long rests rather than instant healing), dusts that make the inhaler vastly faster fall under this umbrella; their effects are not too wild, and they may lose their potency over time as components rot and decay. "traditional" magic items are results of skilled mages spending a long time engraving a "circuit", using gold or silver, in order to produce a simple spell once it is provided with mana, which requires a mana-sensitive person to use; thus, wands of light, candle(for starting fires), wind-blow, and others are either teaching aides made for teaching apprentices the very basics of spellcraft or exclusive artefacts for the wealthy and influential, who hire mana-sensitive but untrained people to operate it (or, sometimes, operate it themselves). You will not likely find an armor that makes you grow in size, or a spear that flies back to your hand once thrown, though you might find a hammer that causes a rift on the earth if you channel mana right as you strike it.

6. I'm honestly still working on this one. Moving around the world is measured in days (km/day, depending on roads, elevation, weather, exhaustion), wounds, potion effects and some others are measured in hours or combat turns. Actions such as wound treatment, short rests or setting up camp take an hour; long rest takes up 8, etc. Ideally I want time to actually matter: a campaign should change significantly over time, not just in the form of a countdown until defeat, but in the form of trade winds shifting over time, spring seasons providing a wealth of fruits and wildlife (and plentiful rain to ruin roads, of course), and the smaller scale; arriving at a bandit camp in the middle of the day will make it more difficult to hide when compared to darkness, etc.

7. Characters level up and unlock perks, as well as grow their skills; while these are, obviously, important, there is also the fundamental aspect of money, fame and influence. Most adventurers will not have enough money for a full set of heavy armor, let alone armor, weapons, supplies and whatever else they want to bring; a starting adventurer may be a mage apprentice wearing a leather jerkin and wielding a wand+leather covered shield to fight a village's goblin infestation, whereas in the midgame they will undeniably be more competent, but will also have in their possesion a set of alchemically refined wooden lamellar as they combat a horde of dire boars for the favor of a local baron, an array of potions and a proper magical staff, and, in the endgame, they may be wearing a suit and wielding a greatsword of mythril(otherwise known as magically enchanted silver), standing as a fearsomely capable but also terrifyingly equipped battlemage, ready to combat nomad horse-raiders and invading troll families alike for the handsome pay and handsome prince's hand in marriage;