A few others, especially for Diplomacy. Back in the day it wasn't unheard of for kings to foster one another's children if they wanted to cement an alliance.

Why must I bribe an oppossing army to get them to switch sides? Shouldn't the spy be able to coerce the general by taking hostage his family? Or the Emissary appeal to said General's Ideology or Ego?

Religion, if I am King, why can't I change it?

Better AI... I am sick and tired of seeing the Byzantines getting their butts handed to them by the Mongols, the Turks and the Egyptians... And the Byzantines initiating a third front by attacking my HRE that is pushing south into the Balkans... They are fighting against Muslim Factions, a Pagan Faction, and instead of calling on support from fellow Christians (albeit from a different Sect) they initiate war?