When sending an Army on a Crusade, if you send the army by sea, the units shouldn't be able to desert. Why? I'll tell you why.

If I have my Crusaders en-rout from England to Jerusalem via the Sea, that means they have to go around the Iberian Peninsula (that's Spain for those of you who are geographical impaired). Hey, guess what happens when they're half-way around the peninsula? That's right, they start to desert... even though their destination was Jerusalem. Are they on their way to the Crusades? Yes. Are they headed directly their? No. So they desert, but if you know of a faster way to row from England to Jerusalem I'd like to hear it.
I can't believe CA didn't think of this.