If you feel like SS is to easy on its own (especielly endgame, just steamrolling the whole world is kinda boring) try out BYG, especielly the new fifth version. Just started out a VH/VH campaign as Denmark and it's really challening. Instead of 2 rounds per year you get 12, feels alot more realistic, supply system, totally different recruitment system, everything feels so much more realistic and much more challenging. Tried to start on gracul AI, but since I, as the player, cant play as recklessly as usual, it was a very punishing 50 rounds since the AI did that. Gangbanged between Norway and HRE and the pope hated me for fighting back, goddamn pope. A really awesome addition to SS if you think its to easy.