Another exploit (sort of), i've just remembered is adding units in a crusade/jihad. The AI can't do that, so it makes the player's effort much much more likely to suceed, while, at the same time, making financial room in his cash flow. This is a potent tool that can be used to say conquer Almohad Spain in a flash. At one time i thought that making the crusade/jihad dependancy at cstle level3, or to make the crusade/jihad marker more expensive and other such that would essentially make the events of Holy War more rare. However, experience with these concepts has shown that they simply make crusading jihading practically redundant. Its much better to leave them on, but switching AI personalities to a non crusader personality (for they do use then holy war as the main tool of their strategy, and far too often), and leave them as they are, while making it an iron man rule not to add units in the crusade/jihad.