Kingdoms
Im not sure if someone already sugessted it.
Kingdoms meant that you can build palace (where kings family lives and ruling kingdom), castles (and other fortposts which is sort of army base), stonewalls (super strong and high walls around castle and cities). That also means that you could have banks for saving people money, regular army for protecting cities and villages, taxes, local markets (not like standart AH in other games, but like sort of big personal storage where you keep your items and sell it in form of market stall or something), police (if needs any lock can be opened), city storage (where u can keep all your valueable items like golden ingots or top weapon), there will be mint which prints kings coins, local territories like county with count in charge and duchy with duke in charge. They are local rulers with their own villages and army, with their own castle and taxes, banks and markets. But obey to king.
Wars
Kingdom can have wars, they can have wars for territories. Some villages wouldnt want to obey and they may become like a cossacs (free warriors without a king but without centralised system tho) Kingdom must protect every member no matter what. if some came to the village and commited crime and hide later on territory of other kingdom behind tall walls, this victim kingdom can declare war if the offender kingdom wont allow to transfer this criminal in the hands of justice. if criminal is hidden on duchy territory then king can allow other kingdom to destroy this duchy in exchange of not having a war to the entire kingdom as this duke has broken the law and peace pack and hiding criminals intentionly. However victim kingdom can let it go cos maybe this case isnt that important to start war based on that. So thats where deplomacy has started. Maybe compisation can be payed off.
Trade and realestate
Also kingdom can have a trades, so all traders can have caravans and trand on other kingdom markets. with proper license ofcourse. there is a realestate market also. top houses withing the city cost lots of money also can be rented. house behind the walls are less expensive yet still costy, prices are going higher as it goes closer to capital.
Lisence
Kingdom can give lisenes for any kind of work on its territory (woodcuting, mining, cooking ect) and police can check license at anytime. If some unkown miner digg in mines other miners can report him and police will come to check his lisence. offender can have a fee on put in jail. Yes also kingdom has prison and justice system.
Currency market
Kingdom will have currency market. Weak currency of one kingdom can be exchanged on strong currency of the other kingdom, say 1 to 20. Depends on economic power of those kingdoms. these exchangers can be both private and state. just buiseness. Also there is an exchange between copper silver and gold coins. they are also need market of exchange. cos its stupid when 1 silver equals 100 copper and one gold cost 100 silver.
Stockmarket
Also kingdom can have a stockmarket, thats where kingdoms (and maybe rich individuals) can trade resources in big amounts, also its the way of trading between local and enterpice producers (manufacturer). You dont expect local farmers to give their beef meat for free, do you? local farmer sell meat to count on a market for cheap price count can sell it to duke for higher price and duke is selling it to kings market for high price. thats how hierarchy works? and thats how money from top goes all the way to bottom. if you wanna sell your meat directly to kings market you gotta have farm near by and be a citizen of this city or to have a special lisence. or if you are citizen of county then just sell to counts market and you might not need any lisence or for very chip price. county market food supply local army but kings market food supply kings army, so if you wanna support kings army you have to buy expensive food so you have to produce more coins. so stockmarket its a place where goods are for sale in bulks by organisation or by individuals. Current market does only sell valube goods like presiouse metals or hq tools. this is liminting market, how about AQ or LQ resources in bigger quantities??? Realm need to grow, workers need money, why cant they supply with basic resources??? everything can be on sale not just one 3000 Q hammer. Say new village whats to be built. they only have 10 Q wood and maybe they collect herbs. So they collect it, sell it, and then buy LQ food. Or maybe they are saving money to buy a cattle. Why you exclude low level economy? now u have to mine cast-iron if you wanna be supplied only by the market cos thats what is everybody needs. what about the rest of resources??? in other games with common AH their system doest it for you, but here realm can be a huge resource hub with huge undeground storages and you can exchange your basic labore and get the rest of what u need. maybe you only like hunting or deal with cattle or just grow carrots, maybe you wanna be a biggest carrot supplier, you dont wanna do everything by yourself, u like only one thing, and why this work cant support your living?
Castle
Castle its an army base. in case of attack all viligers can hide in castle (maybe even teleport there) so offender realy have to destroy castle to destroy all village citizens. he can destroy village but not citizens. and village fighters recive alert that they are being attacked. so they gotta stand for the village. Count village or castle can request help from duke or kings army. and they will. cos they pay taxes which support army as well.