Replacing France as the protector of Pope Country, and even using religious pretexts to criticize Italy in public opinion, primarily delays the process of Italian unification, which is greatly tempting for the Austro-Hungarian Empire.
Although Pope Country is now very small in size, it's not just any region but Rome, one of the most economically developed areas in Italy, with unmatched cultural, historical, and political status. Economically speaking, the most developed were Venice and Lombardy, former territories of the Austrian Empire.
Ernst merely proposed a rough plan; to turn this into reality, professionals are needed to refine the details. Just catching Franz's attention means half of the work is done.
...
"Ernst!"
Ferdinand called out to his future son-in-law just as he was leaving Mei Quan Palace.
"Father-in-law, what's the matter?"
"Do you have some grudge against the Italians? Coming up with such a nasty idea!"
