Another option against the Sicilians (gotta love my people!)

If you don't have a provincial boarder with them, all you have to do is seperate yourself from them. Pull your ships away from ALL of their provinces (sucks but if trade and transport are kaput anyhow, all those ships are is expensive drift wood) and away from any SIC ships you may find. If you can get to a point that NO units you have are in/near their provinces and you're not sharing a sea zone with any of their ships, after one year of inactivity they go back to being neutral.

That doesn't compensate for the revenge you'll need to wreak on them later, but at least it alleviates the need to take the pope out in the process. I'd pull back, gain neutrality, then land a wrecking ball type stack on one of their biggest provinces and pillage and burn them into submission.

iBuen Fortuna!

A