Some points!
While i do agree that WE isn't as good as it could be and doesn't fully represents all the aspects, it's really hard to add new modifiers to it and keep everybody happy and the motive coerent.
Now, i am for WE to be influenced by the religion of the combatants, the initial ones. If they differ in the sense that are incompatible or oposed, the defender should have an advantage.
Next, while nationalism is not an issue, there was at the time a sentiment of pride and fame, and even the poorest peasent would bragg if in a foreign town about the war won by his curent ruller against someone else who dared to upset him. Peoples generally hate incertenty, and a posible change in rulership could bring a lot of bad things. TO make it short, people will tolerate a somewhat prolonged succesfull war, and at the same time won't run hiding if there are some defeats.
Therefore i'm for some deduction in WE for a victorious campaign, perhaps also dependant on the raport between your loses/their loses. One more thing, given the curent rate of WE, it should really kick in only after 2-3 years, and it may stay at the current rate.
After all, armies must move, skirmishes take place, generals must do maneuvres, cities change alegiance, spies must do their thing, indecisve battles must take place, men and reinforcement regroup, news arrive from the front...news dismised as inconclusive, rummors spread, both bad and good, heroes are born....and only after some time resentment begins to apear, in the begining only whispers, then it grows, at meetings and in inns talks about the taxes and bad shape of the army are heard, resenment grows....and only after some more time nobles makes their voice heard, people comes to the street, people yell and spitt the oficials.....people atack oficials...people stop paying taxes...people rise in arms!
Call me creazy but all this seems to hapen in 3 years EU II time!