Chill_ean_GUY
Yo author I think MC should send Somme Finn's in Ibben. And slowly conquer it as an backup ground for the kingdom of Prussia. According to ASOIAF wiki Ibben has, "Gold, iron, and tin are abundant in the mountains of Ib, whereas timber, amber, and hundreds sorts of pelts can be found in the island's forests. Whale bone, blubber, and oil are Ib's chief stock-in-trade". I'm sure the above information can help the Prussians greatly in the long term. Hope the info was helpful.
I love the detailed writing on world building. I love the way the story progresses”its pace”. I love a-lot of the characters. Onto some ideas Breeding of crossbred horses and plants to get better effects out of produce and travel. Speaking of travel you can add railroads only in your lands. The spreading of religion through the lands. A conflict with the faceless men, the prussians have been there long enough for the faceless to know their language and customs.