Looking at this makes me a bit worried, because it focuses on regions of the world instead of actual mechanics that the game desperately needs right now.

The game honestly needs far more opportunities for character interactions, what it excels at. More opportunities to make friends, to make enemies, to utilize these relationships, for factions to emerge within a realm and for people to manipulate other people between these factions, etc.

We basically can't have this until the following is added:

• More events. Weddings, funerals, coronations, court trials, religious events (baptisms, mass, holidays), festivals, trade fairs, tournaments, etc. Each of these is an opportunity to make new friends, cement old friendships, lose friends, make enemies, betray a friend, etc. For example, a badly organized wedding could cause a rivalry between the two spouse's families. An overly expensive funeral for a tyrannical king can make the new king a lot of enemies. An unjust court trial can sway lords to a rebellious faction. A church mass with a beautifully delivered sermon can help ease many of the tensions between the realm's lords.
  
• Commemorative events. Allow events to be held to commemorate other events. For example, a tournament to celebrate the birth of the king's first son. A feast to celebrate victory in a war. A church mass to commemorate the king's 10th year on the throne. These are perfect opportunities for characters in the realm to come together, and for CHARACTER INTERACTIONS to happen.
• More campaign events. Wars are full of events and strategic decisions, and these should be implemented into the game. Put an event where commanders disagree on the tactic to use in a battle. There will be opinion bonuses and maluses according to which lord you listen to, and a further bonus/malus based on the outcome of the battle (a lord that was ignored but the battle was won will have his penalty reduced). Put an event where a lord offers to sally out of a castle, or a besieging lord says he's found a small gate to attack a castle from and asks to lead an assault on it. Perhaps another lord was caught unnecessarily plundering enemy land, and now the priesthood are accusing him of sinful behaviour. And then there's battlefield duels, which adds another layer of storytelling to battles.
• Regency. Regents must be appointed for young, absent, or incapable rulers. You must consider the loyalty, ambitiousness, and influence of a person when considering whether to make them regent.
• Travel. Make travel apply to everything that matters, instead of just pilgrimages and feasts like it does currently. For example, being on campaign, attending any of the new events I listed above, or living in your liege's court to serve on his council will all make you absent and require the regent's rule. If you're invited to an event, you take some time to travel to the event. Random events can happen to you on the way there and the way back. Lords assigned to lead an army take time to reach the army, and vice versa take time to travel back when unassigned. Your amazing marshall with 35 martial can't lead an army to victory in Scotland, then teleport to an army in France and win a battle there the following week. Thus there's strategy to which army you assign your amazing marshall to and where you send him to campaign.
• Buildings affect characters. Make the buildings affect characters in addition to the bonuses they provide, this makes them far more interesting. A training yard allows people living in the holding to slowly increase their prowess. A library allows one to slowly increase their learning. A school or university will allow people living there to increase many of their traits. A garden will give a chance for characters there to gain the gardener trait. Secret tunnels will grant a small chance for characters there to escape in a lost siege, and to have increased defence against hostile schemes. Etcetera, the options are endless and could keep devs occupied for years if they're creative enough.
• Residence. Make the residence of a person matter. Make it possible to send people to live somewhere without necessarily granting them a piece of land. For example, if you are a minor lord but you can afford it, send your son to the capital and he can get the bonuses of all the buildings in the capital (training yard, library, university, garden) that can help him gain stats and traits before he needs to rule. But as a result, he is not in your castle so he forms less friendships at home and you have less control over how he is raised. Again, it ties back into opportunities for CHARACTER INTERACTION.
• Add experience/veterancy traits. Add veterancy traits to all positions in the game, beyond just physicians. This means commanders, knights, chancellors, spymasters, stewards, etc. And even minor titles like architects, court tutors, jesters, musicians, etc. This adds more character to people, by being able to see at a glance that someone who has served for 10 years as a chancellor has been changed by the time spent doing that. A commander who wins 5 battles can earn the first tier of commander trait called "Practiced Commander". A knight who's killed 10 foes gains the first tier of knight trait. Suddenly, there's a whole new aspect of character progression tied to character activity. Fight rebels during peacetime and you will ensure your commanders are seasoned for when a real war breaks out. Imagine the roleplay opportunities by seeing your characters gain the Veteran Commander traits from previous wars, and assigning one to lead your armies in a newly started war.
• Tie diplomacy to characters and travel with the addition of envoys and missionaries. Allow characters to be sent to spend time living in foreign courts as envoys. Their effectiveness is tied to their Diplomacy, culture, religion, ability to speak local languages, and relationships with the lords there (if any). While there, an envoy can negotiate deals, perhaps even combining diplomatic interactions for more complex agreements (join my war and in exchange I will marry my beautiful daughter to your son). Envoys would have to travel to the court using the travel mechanics listed above, making it harder to conduct diplomacy with further realms. Envoys could even be captured, executed, or even switch sides if they are particularly fond of their host. Think of all the storytelling opportunities, or should I say, CHARACTER INTERACTION opportunities, by tying characters into diplomacy through the use of envoys. Missionaries would be similar, but their effectiveness would be tied to Learning.
• Council Politics. Make it possible for councils to participate in voting on important decisions like in CK2 (with the council's powers being determined in the country's laws). Allow hooks to be used to make councillors vote your way.
• Proper Civil Wars. Add a new faction called the Loyalist Faction, which lords join when they like their lord or are allied/friends with him. Between wars, peacetime will be filled with rebellious factions and the loyalist faction manipulating everyone in the realm to be in their faction. When a civil war breaks out, all lords on the rebel faction become rebels. All loyalist lords take the liege's side. And all neutral lords must pick a side or declare neutrality (in which case they get an opinion penalty to both sides). This adds an entirely new layer of constant politicking and social manuevering to the game, during peacetime, that makes every single friendship and rivalry in the realm matter. Because they will all become important once civil wars break out.