I like the idea of sending armies to do a crusade - but there is no control over it and the leader is being selected randomly. I'd like more influence on crusades, like joining a crusade, abandon it, delay the decision a bit, etc...
Yesterday i was going to siege a town with my marshal and i got a notification to lead it - my marshal immediately dropped all the troops and started beelining to the crusade target. Today one AI marshal got selected to lead the crusade, he went there, got his bottom whipped and the crusade was over. I'd like to join these if i'm not leading it, participate, help them, maybe even taking over leadership if the original leader dies, etc...