may be missing the point but so what if you have a crap reputation. You know that regardless, slowly, turn by turn the AI will double cross you, stitch you up, and forge impossible alliances especially with muslim factions to war against you the catholic one (no excomm). Everyone will hate you and attack once you border them and it will happen whether you are the hero or the villian. Diplomats do not work effectively after trade agreements at the start and serve no purpose at the latter end. you cannot bribe, obtain a ceasefire without paying some extortionate amount, or arrange a marriage without paying a extortionate amount, and alliances well you may as well invest in your own military machine and save the effort, Reputation might as well not be a factor of the game