What about a situation where the Schmalkaldic League win their war and manage to extract codified rights for Lutherans in the HRE, i.e. the first (?) Diet of Augsburg, but manage to remain strong and don't dissolve the alliance but instead make it a kind of Protestant faction in the Diets, strengthened by further defections to the Protestant cause if it seems that the Protestants aren't going to lose their rights any time soon. I think there's a possibility, given the initial ruling that converting Bishops could keep their territories, that one of the Electoral Archbishops could convert (I believe that a few of the Archbishops of this era were born Protestant and later converted, they could easily have done this for show, and then converted back when they saw the advantage) which gives a stronger Protestant position in the Electoral vote situation. If Hesse shows leadership all the way through the war, they could maybe become an unofficial leader of the faction in petpetuity. Could this work?