Ummm, the idea is actually an old one...
That a sort of “Confederation of the Holy Lands” would exist, with a Jewish state of Israel, a Christian state primarily of Lebanon, and a Mohammedan state of Palestine all three co-extant with a capital at Jerusalem... with a prime minister the head of government chosen by a College of Electors, and the head of state being the Roman Catholic Pope...
The idea being that such a tri-partite state would provide a check-and-balance system akin constitutionally that would cause all three to propser only jointly, not separately.
Jerusalem as an adjunct to the Vatican is an interesting modification of that.