Your challenge, should you choose to accept it, is to make Denmark very powerful/dominant in northern Europe by 1300.
Parameters:
1: A union in which Denmark is an equal member is acceptable
2: They must have at least 5 regions outside of Denmark, Scania, &Schleswig-Holstein- Finland, Ireland, Wales, and Iceland count as 1/2, Scotland, Norway, Sweden, the whole modern Baltic triad count as one, England as two, France and Germany as three, etc.
Bonuses(Largely mutually exclusive):
1: Make at least the majority of Denmark and the rulers pagan, if not the whole empire.
2: POD after 1066
3: Danish Constantinople
Am I asking too much? Is it outside plausibility?