I like the idea of entourage acting as defenses for particular lords, preventing certain actions or increasing their costs. I'll have to see what works and what doesn't, and add in the inverse, some lords being particularly weak due to have ineffective entourages. Some of these bonuses would probably then pass over to the player, for example if a captain of the guard were effective they would slow the rate of population uprisings, provided they were still loyal to the lord.
Adding buildings which increase power regen at the cost of world evidence would probably also be a good idea. Those certainly shouldn't be too hard to implement. Might make one which is ritual based, so you can choose when you're okay with gaining some suspicion/evidence/world-evidence and when you feel the heat's on and you gotta lie low for a while.
In regards to some of the other stuff:
Back in the day, in the very first concepts I did in late January over the course of a week or so, the game was very different. All lords could plot at all times, not just the player. Every action available to the player was available to everyone else. To add to this you could only interact with people you had a direct connection to, but could persuade others to become loyal to you, so use them as gateways to others. For example you could try to gain access to the king by first convincing the queen's chambermaid to support you, then use the chambermaid to convince the queen, then the queen to convince the king. The reason the game is so radically different from this idea is due to the insane amount of chaos it produced. It was almost impossible to keep track of anything, with many plots ending every single turn, which would mean that your own plot was now completely useless or impossible, and the giant network of people was a nightmare to get on the screen.
As a result, I'm unsure I want to try making all other NPCs have their own plots, or have a "discovery" mechanic for information. I've no doubt it would make for a good game if it were implemented, but I'm personally not sure I know how to do so successfully. I've actually got a document for "ideas for a sequel" which are ideas which I don't think I can risk spending the time on, in case they completely don't work and just harm the project as a whole. I'll add the infiltration and discovery mechanics to the list, and maybe someday they'll see the light.