Sweden
In early 1470 Sweden is ruled by King Charles VIII. However, he is destined to die next month (in game), so I will write this post from the perspective of Sten Sture the Elder, a Swedish noble Charles's heir and (historically) the next ruler of Sweden for the next 30 or so years. After Charles's imminent death, Sweden passed into a state of revolt against the Kalmar Union and King Christian Denmark). (The link is weird. Add another ) to the end of the url.) The war was largely decided at the Battle of Brunkeberg outside the gates of Stockholm where the Danish forces were outflanked by the much larger Swedish peasant levies. This victory secured Sture's position as Regent of Sweden and made him the Lord Protector of Sweden (Riksföreståndare), as well as making Sweden temporarily independent. At this point in the game, however, all this is purely theoretical. Sture was known as a very diplomatic figure and managed to maintain a balance of influence between the more rowdy peasants and lower nobility, and the more conservative clergy and upper nobility. He also effectively negotiated for increased Swedish autonomy when King John II Denmark and Norway was officially declared King of Sweden in 1483.
At this point in history Sweden controls most of the current nation of Sweden with the addition of most of Finland, and with the subtraction of several provinces under Danish control, including Småland, Gotland, Skåne, Jamtland, Lappland, and Bosulän. As Sweden, I would make it a priority to reclaim these provinces from their Danish oppressors, or the native populations that control them.
In its current state Sweden has little to no active military and was only able to muster a few hundred actual soldiers before the Battle of Brunkeberg. Its economy is largely agrarian. Sweden is rife with internal politics and feuding nobles, some of whom support the union with Denmark, but most are in favor of independence. Most internal decisions are subjected to the Riksgad of the Estates before it is ratified. There are four "estates" represented, namely the nobles, clergy, merchants, and peasants. In terms of foreign relations I am less sure. Sweden is cautious toward Denmark and Norway as they are our largest neighbor and have immediate cause for war. I believe Sweden is also cautious towards Novgorod due to tensions over Finland, but I may be wrong.
The objective of this game is to lead a nation from the late 15th century through to however long it runs.
I do have some experience with EmpirePowers. I was the first Brittany in the last game of this. Example of RP from the last game.