Other factions that played an important part in the crusades were of course the Byzantine empire and the jews. This brings us to an interesting dilemma and I would like to know how you would solve it.
Considering the fact that the campaign is of good vs evil in nature how would these factions be seen? During the first crusade the jewish and muslim populations of Jerusalem fought together against the crusaders. Crusaders (the good faction) massacred both the jewish and the muslim population of the city. It just makes me wonder if this makes the jews evil too?
On a way to the holy land during the second crusade the do-gooders massacred the jewish population in rhineland. It seems clear that crusaders saw the jews as their enemies but is it enough to define the jews as evil?
Btw murdering defenseless civilians is kind of difficult for me to see as a good deed but maybe I have a lot to learn about this good-versus-evil thing. Or maybe they just atoned later?
During the fourth crusade Constantinople the capitol of the Byzantine empire was sacked. A crusader kingdom like in your campaign was formed. There must have been a good reason to attack the city as forces of good would not do such a thing otherwise. Or would they? Maybe the Byzantines were evil too?
I know these are big questions but as we know you have done comprehensive research on this subject so I trust you have well founded answers.
I have only one answer. Good and Evil are a representation of personal belief. The Crusaders who did these atrocities you are talking abotu did not see themselves as evil any more than the turks thought they were evil, or the saracens or the Nazis. Are they evil? Depends on who you ask.
And you are talking about the reality of history and a game setting. The atrocities committed by Amico during the slaughter int eh Rhineland were horrid and uncalled for (even without going too far into today's mentality of the great white guilt) and was criticized by the church as well as the major leads of the crusades. During the Thrid Crusade, Phillip, Richard and Frederick went through great pains to ensure another similar event did not happen.
The Fourth Crusade was also a disaster that ended with the sacking of Constantinople because the expedition ran out of money and the Genoese and Venetian merchants who were funding equipment, transportation and other supplied for the Crusades wanted their money and more or less forced the crusaders to sack the city to get their money.
However, in this setting there are no Solans living in the southern realms (at least in great numbers) and there is no counterpart to The Eastern Empire.
Lastly I want to reiterate that the idea of good vs evil is based upon what view and side you are one. The religion of Jove decalres sorcerous magic to be in general evil, therefore its practitioners are evil and so on.
The acts of barbarism in the crusades were often from desperation, greed and other machinations. Does that make Christianity evil? A desire to "liberate" their sacred city from the "infidel"? In todays morality, yeah it does, but we are talking 1000 years ago.
And for the record, after the second crusade and leading up to the third crusade, the Jewish, Christian and Muslim populations of Jerusalem banded together to fight Salah-A-Din and his invading force. Sure, they were not slaughtered to a man but those who could not pay a ransom were sold into lifelong slavery.