I think anything else but the CK 1 naval system is an improvement. There is a reason why the Kings of Denmark and Sweden had to content themselves with converting pagans, whilst the wealthy and relatively well suited Kings of England and France (and the Holy Roman Emperor) went after the main trophy (Jerusalem!). Naval combat in the Mediterranean had become way too expansive to the Danes and Swedes.
As for naval battles not being decisive. I would say that the Battle of Sluys was pretty decisive, because it had long term repercussions for France. The English victory dashed all French hopes of securing an early victory in the Hundred Years' War and opened the way to an English invasion of Picardy (which bore fruit in one of the most decisive land battles of the Hundred Years' War, Crecy 1346). As for the English not being a naval power in the Middle Ages, I would respectfully disagree. A modern sense of naval power didn't exist (and yes, the Royal Navy didn't exist). But the Kings of England had given considerable freedom to the Cinque Ports (Hastings, Dover, New Romney, Hythe and Sandwich), a group of ports along England's Channel coast. They were given charters with extensive rights in exchange for providing ships for the King. Apart from the leidangr in the Viking Age and the navies of Venice, Genoa and the Hansa, I know of no other organised naval defence in the Middle Ages.