Well, Erik VII did fight a few battles in Sønderjylland (which is to say Southern Jutland and Holstein) against the local nobility (they were never too happy with the central governement).
However they ended in a draw (well, a slight victory to Erik actually) and a peace was made. A peace where the conditions weren't kept by the nobility and another war broke out. This time the nobility was aided by the Hansas and there was a major sea battle at Copenhagen which the Danes won. However at land much was lost, and the concessions gained at the first treaty was lost. Erik then got fed up with being king and became a pirate operating from Gotland.
This means that the main operations at sea was after he descended the throne - so maybe one should just give him some mediocre stats and make him a land leader?
Christoffer of Bavaria .... he had some serious battles with the peasants of Northern Jutland ... at first he lost, then he negotiated, and the ones left were crushed big time.
Anyway ... I think that was all of the leaders of the 15th century ... when there is an agreement here we can move on
Christian I led an assault on Stockholm personally and was soundly defeated ... not much to brag about there I'm afraid. - But according to Arilou he had a general (well, a noble of cause) of some sort who appearently were quite succesful.
The Swedish King Karl Knuttson Bonde, did a whole lot of rebelling but never to that much avail. He made some raids into Skåne but never did much damage except some random looting. He never sieged anything either. I could easily see som low leader stats for him (if he should be kept at all).
Engelbrecht. Well, he never really got the chance to fight anyone I guess. So the fire and shock values would pretty much be anyones guess. So I think we might as well keep them at average (2/2/2) - and then the one 1 siege value. However he was a rebel leader, so he should be given the lowest rank possible (if he hasn't already got that).