Wild thoughts.
1. Especially for tribal, start as barons, and have to develop enough to have a county.
2. Why do lieges never travel? Historically, lieges would spend time travelling to vassals and their other holdings. There could be huge event possibilites (plots, WOL, etc.).
3. When holding castles, what about appointing seneschals for those holdings. Maybe a law setting similar to viceroyalties, and/or minor offices?
4. Plots and decisions based on being an officer of your liege. If I'm steward, have decision paths on how to improve the economics of the realm; if I'm spymaster, setting up agents for the network; if I'm court chaplain, and the king becomes a heretic, work to overthrow him and/or counter his decisions.
5. Random bastards. I've never seen events with a child showing up as the bastard of the king from a scullery maid. Decision trees for rule/officers to hide/raise/kill child, mother can be off stage.
I'll go back to lurking now.