1. Poland was divided into districts only in 1138 so it had no vassals but I understand that this would mess up the balance.
2. The capital of Poland since 1039 is Krakow. Right now there is some city that has never been the capital (Crinsk or something similar, I don't remember because I've never even heard of such a city before). If Krakow can't be the capital of Poland because, for example, it is the only region of Lesser Poland (Lesser Poland Province is a vassal of Poland), then I propose that the capital be Gniezno, which was the capital until 1039. As a Pole, I can't stand the fact that the capital is some Crinsk

3. The province map. When I switch to the province map, playing as Poland, Poland has provinces in very similar colors and I can't tell where their borders are. In Empires it was more visible because the colors of neighboring provinces had more distinct colors.