I might consider getting into M2TW modding again.
But before that, I'd like to hear people's thoughts on my idea that I think is "crazy and revolutionary" - or so I think. It's actually not very revolutionary, as it is a clearly stolen idea - inspired by the Estates from The Cossacks DLC for Europa Universalis IV, though I did have something similar in mind back in 2011 or so too.
The basic idea is that each province you own would belong to someone within your faction: the ruler (YOU), the nobility, the burgers, the clergy or the free peasantry (yeomen?) and the knightly orders. Castle-town distinctions would be abolished.
The Six Estates: Royalty, Nobility, Clergy, Burghers, Yeomen and Knightly Orders
Royalty
Normally, when YOU - and your close relatives (the royalty) - are the one and only owner of the province, you can only recruit mercenaries, a limited amount of peasant levies, and maybe some unique units. You get all the income, loyalty is normal.
Do note that the option to recruit mercenaries, limited amounts of peasant levies and the unique elite units still stands even if you give the province to one of the other five estates.
Nobility
Giving the province to the nobility would grant you access to elite units - for Europeans, that would mean Knights. Mounted and Dismounted alike. For the Moors and Egyptians, it would be Arab Cavalry, Mamluks (Egypt-only) and Jinetes (Moors-only) instead. For the Turks, it would be Sipahis.
However, it would reduce income you get from the province, and since medieval nobles aren't known for being the most loyal folk - oath or no oath - the province's loyalty would be reduced.
Also, Knights, Arab Cavalry, Mamluks, Jinetes and Sipahis would become general bodyguard units. In other words, when you are hiring one of these units, you are also hiring a general.
Clergy
Giving the province to the clergy would allow you to recruit more priests, make missionaries more effective, make education more effective (acting like a sort of university, a la Stainless Steel), and if you are Catholic, the Pope will like you much more.
The Church doesn't have a reason to betray you, so loyalty is increased (chances of peasant rebellion lowered). I am not sure if trade income should be lowered or increased - while in practice, you lose sources of income by giving away land to the Church, the clergy have historically made fine governors and economists... besides, game balance - we gotta give players incentive to give some land to the clergy!
Also, for the Danish, this would unlock the Norse War Clerics.
Burghers
Giving the province to the burghers would give you access to militia units - Spear Militia, Crossbow Militia, etc. - and for Catholic Eastern European nations (namely, Hungary and Poland, maybe Denmark and HRE as well), the Burgher Pikemen would become hire-able. Oh, and the dreaded Merchant Cavalry Militia would be hired here as well.
Additionally, trade income would increase, but along with it the chance of your governor gaining negative vices. Not sure what to do with settlement loyalty / rebellion chance.
Yeomen or Free Peasants
Giving the province to them would first and foremost decrease your income, but would drastically increase province happiness. It would also allow you to hire Peasant units in higher numbers: Peasants, Peasant Archers, Peasant Crossbowmen - maybe Peasant Spearmen would make a comeback, being given to all factions rather than just the junk Saxons. For the English, Yeomen Longbowmen would be available here. For the Hungarians, you would get Slav Levies (or something similar) and Magyar Cavalry.
Maybe the income shouldn't drop - as peasants who can manage their own land are much more motivated to work harder - but you know, game balance...
Knightly Orders
Only available to Catholic factions, replacing the "guild" orders, you would be given the opportunity to give the province to the Templars, Hospitallers or Teutonic Knights, giving you access to their special units (Templar/Hospitaller Sergeants-Crossbowmen-Gunners, Templar Knights, Hospitaller Knights, Teutonic Halbrüders-Ritterbrüders-etc, etc.), and some nice bonuses.
How do I plan on implementing this?
Via buildings.
Simply having buildings named "Estate Grant to Nobility", "Estate Grant to Clergy". Then I would have Stables, Archery Ranges and Barracks, so I can tie recruiting the units to having the estate - Stables, Barracks and Archery Rangers would offer no bonuses on their own, so that the game won't crash by adding a building requirement to unit recruitment.
Alternatively, I could just tie the unit recruitment to the estates, and make the estates upgradeable, increasing their advantages as the settlement develops.
The original MTW had a building named "Baronial Court" that could be upgraded to "Baronial Estate". The earlier would unlock Feudal Knights, the latter Chivalric Knights.
Back in 2010-2012 - before I encountered EU4 and it's DLC - I had the idea that you would be able to build multiple estates in your province, but doing so would result in the province slipping out of your hands for all practical purposes - you would lose nearly all income the province offers in exchange for the bonuses the estates would grant.
My current idea is simply one estate per province.
Not building any estate would simply mean that the province is in the hands of the royalty - maximum income for you, neutral loyalty, but no noble knights, no burgher militias, etc. Alternatively, the lack of estate building could represent lack of proper administration, and the royalty would have their own estate building as well, providing bonuses I did not come up with yet.
Your cents?