I always scoffed at the citadel as well, that is until I played a game with Isabelle and had CR3 cannons being produced. Nothing stops them. If you play as her you basically want to focus on having a war during that era. Conquistadors are decent, coupled with huge cannons you can do some serious damage. Just delay economics and head towards rifling to finish the job. You can pretty much end the game during this era with a mass rifle draft, your cr3 cannons, and conquistadors.