Any ideas or critics about the suggestions are open, tell me if something is missing or you want to see too. I have also studied many medieval cultures and technology, so most of the random things should be fitting with the game age. I am also trying to keep this to a simple crafting method for simplicity.
Now before I get into the first one, yes, I know you can spawn NPCs as a GM, this idea came to me while messing with portals and complaining that all my NPCs were killed in town.
The idea is to make a gate that you can "Summon" NPCs by spending coin, there would be 3 types of NPC the Citizen, Town Guard, and Perimeter Guard, all spawned without gear and must be spawned on a deed(Taking up a citizen spot), after which only the mayor or top ranking members may edit the items and name on the NPC. The Citizen is more for RP and will act like a normal spawned human, its to bring more life to the area and should be the cheapest, maybe 20 copper or a silver and will stay within the main area of the deed, might be fun to "tax" them to help for upkeep. The next would be the Town Guard, they will act as the main defense against monsters and hostile players on the deed, with moderate skills for fighting and should respond like deed guards, they however will not respond to cries for help, they should cost 1 silver to roughly 20 and draw a salary similar to other deed guards(Though honestly they might be more useful than normal deed guards if armed properly). The last is the Perimeter Guard, this one is similar to tower guards and will come to the aid of friendly units and citizens in on the deed and will also move around the perimeter to help keep the town safer, this one should be stronger than the town guards and should cost more as well as draw a higher salary.
This is a similar idea to another so I will add it in that maybe there can be a 4th and 5th "Type" adding adventurers as pet-like humans that will follow the player into battle and bandits, which would be uniquely spawned from a different portal(highway stone) that is off a deed, instead of helping fight they will attack nearby humans other their their "boss".
Wealth is Power
The idea is mainly to be used in a well developed server or heavy RP one, allowing bars to be made of precious metals(or any metal), coin blanks, and more importantly, unique coins. This is more built for player run economies that are separate from the generic "coin" values. A person can make the coin blanks from lumps(or bars), then use a coin die that is uniquely made to strike a coin unique to the die. The Bars are more or less a "trade" commodity, though they could be a step to making the blanks and should weigh 5kg each, they could also have smaller bars weighing 1kg and .5kg(this one is more suited for making coins).
I can imagine this being a great addition, seeing a server with 3 kingdoms each with their own currencies, maybe kingdom a wants to stick to only one coin and calls it a Septim(from the Elder Scrolls), another wants to have a currency based on the roman solidus(gold), siliqua(silver) and nummus(a small copper coin), and the third may be more suited for the in game currency, the idea is more for larger servers, though imagining multi island servers trading at ports and exchanging currency would be a rather fun sight. This would also make the coin die a vital point of a kingdom and currency, it shouldn't decay or at least to the point of destruction.
Magic and Stuff
While this is not likely to get into the real game, I wouldn't mind seeing this in a mod. The ideas are more based on alchemy and the brewing of healing items and minor potions(not the blood ones), items like salves(yes, I know about Farmer salve), tonics, elixirs, and distillation or extraction of material like salt. Salves are made to help heal wounds, though I was more looking towards a specific wound like a bite salve or a burn salve, rendering them useless to other wounds. Tonics, one of the "potions" of the group is a direct healing item, though not as good for heavy wounds, it is instant(aside form a 2 second drink) and heals any type of damage as long as its not infected. Elixirs are the more buffing version of the "potions" family, instead of instant rewards it can reduce times of some actions, increase healing, even slight speed boosts, but wear down faster, lasting only a few minutes or a few seconds in some cases. Tinctures are the last "potion" time, and are like tonics, but instead of healing wounds, they do immediate special effects like removing hurting, curing disease, restoring stamina, and maybe even remove an infection(though the wound would remain). Tinctures need distilled alcohol to make, which is obtained at about a 10% rate from wine, so make sure its worth it. Oils are next, they are materials that are applied to items and weapons, using olive oil as the base, giving a small benefit to the item or making them deal a special damage, like poison, acid, or fire.
The next is a bit different, it involves making magic parchments, these are designed to have a spell cast on them similar to vessel, increasing the difficulty of the spell by 10, but allow you to store a spell in the parchment, the spell must succeed to enchant the scroll, failure costs the favor like normal and quality of the paper. The scroll will have a single use and is castable even as a follower, so long as they are of the same faith, but the spell may still fail, the casting of the spell will be 20 points lower on difficulty. On the other hand, those with karma spells can also make scrolls, but at the cost of double the karma, the benefit is that no staff is needed to cast the spell. This would make these very valuable. I also wouldn't mind a "wand" being made that can hold charges of a single spell up to 10-50 charges, similar to a scroll, but requiring a shaft of wood, being enchanted and then slowly charged with spells, the downside of a wand is minimal, though the difficulty may be raised a bit more.
Common ideas and not so common things
This is more of a rough item list. First Glass, why do we not have any glass, this is such a common item, even back in dark ages and can be made easily using heated sand and maybe purifying it with some ashes similar to steel, glass is resistant to decay and would likely be very useful for long term storage, but cant be made to large. Glass flasks, bottles(use a peg to cork it and keep the liquid from decaying easily), goblets, bowls, orbs, alchemical glassware, etc as well as colored glass. Pewter, a common metal in old times, easily made with lead and tin, though not healthy to humans, it works for poor utensils. Slag, this one is a little different and isn't very useful to most people its more of a waste product that is made after melting ore, that said, it does have historical use as a concrete additive and can be used for that or if all else, make stone shards be a byproduct.Other small ideas are like making book bindings to hold sheets of paper, scrolls(I don't mean magic ones, literally, why has this not been a thing?) that can be sealed, Signet rings that can be used to seal scrolls with bees wax or mark papers with an official seal. Other ideas is to remove the metal restriction on utensils, allow metal plates, cups, flasks, jar(urn), bucket, rings(I actually wear a steel ring, heh). Other alcohols like vodka, beer, brandy, rum, cider, mead, etc as well as make wine not require maple. Daggers, why no small sharp blades to stick the enemy, or throwing daggers, throwing hatchets, throwing hammers, throwing spear/javelin, slings, crossbow, bolts, rapier(A sword designed more for poking holes instead of slashing), spiked flail, a wooden club(peasants rejoice), scale mail armor(scale plates are stronger than chain, but weaker than plate) etc. Oil pot lamp, a simple clay lamp that uses tar or oil to light a small area cheaply.