Pity, I really liked my Warrior Priest leading his army, even if you know he couldn't lead any troops himself, or actually enter the battlefield to use marshal settings.
Historically, priests have acted outside the authority of the military because the Vatican has been so powerful. The priest would not lead the army, but would indeed hold a very high position among the advisers to the military campaign (and probably provided much of the financial support).
(yes, I know, this isn't a history simulator)