If anyone is still interested in medieval era RP - check out Persistent World, a mod for the popular game Mount and Blade: Warband.
It offers huge maps with player-run factions, up to 200 players (I've had some epic 100v100 player battles). Diplomacy, farming, smithing, any profession you could think of. There are two main servers, one oriented more around gameplay and one oriented around roleplay. Maps are built up out of various castles, mines and landmarks that the different player-run factions can try to grab or defend. I've had some fucking amazing sieges where hundreds of players are all participating, making shieldwalls to try to approach a castle while the defenders try their best to hold it with a shit ton of archers.
On top of that, there is an economy system that actually works genuinely really good. Every castle has its supply of resources, any player can buy or sell resources to those supplies, as you sell more resources, the stock goes up. Generally what occurs is for a castle to hold lots of player knights for instance, it needs a lot of armour, swords and shields in stock. The issue is, if people buy this stuff but it's not being produced, it eventually leads to the items going out of stock. This means that every faction needs to make use of Serfs (the only class that can gather resources, such as through mining or chopping down logs), blacksmiths and other armour-making classes to produce the stock of their castles.
If you are a serf, you lead the risk of possibly being robbed by either opposing faction members who just wish to be hostile with you, or even Outlaws. Outlaws is it's own faction, and Outlaws are a sort of lone-wolf playstyle, you can basically be a bandit and steal from common folk and rob them. This results in factions having to protect their serfs to ensure that their resources do not get stolen.
As I mentioned earlier, all the castles have different prices for goods, so you could even be a merchant, buying resources for cheap and selling them for high in castles that need those resources. Food can also be made through farming, which is a vital resource during war time, as food increases your health by quite a substantial amount. A well fed army will usually win the battle when it comes to a sheer numbers battle. That is why it's important to protect farms outside of your castles, and to try to increase your factions influence on the map.
Being a serf isn't boring either, because you make a shit ton of cash doing it, which means once you do switch to being a soldier, you'll have lots of money to spend on the best gear. As a farmer you can sell carts of food to local factions for money aswell. Serfing is the prime way of making money, which then lets you transition into becoming a soldier whenever you'd like.
The battles in Persistent World get pretty crazy, when I used to play it I was in a big faction with roughly 90 or so players, we'd all be in teamspeak and all move as one unit, we'd have different segments of the army, footmen, cavalry, archers - as they are all vital to make an army strong. I can not describe some of the fucking awesome moments I've had, seeing hundreds of players march in formation and seeing two armies clash is honestly fucking amazing. The epicness as individual 1v1's occur while archer fire covers the field with arrows and cavalry tries to snake their way through the chaos to pick off stragglers is honestly something that no other game could deliver as well. What makes it so cool is the fact that every single person is a player in this giant war.
Some videos
Skip to 10:30, every character is a player there, and that would be considered a small siege compared to the total capacity of most servers.
20:10
