[P3D]

You need the Kohen Gadols for the Divine bless.
You could replace them by Kohens casting Blesses instead, of course. You most probably won't have standalone 800 gold temples to recruit indie priests instead of just more Kohens.
Further Alternatives are a Kohen with Crystal Shield or four-six Kohens with communion/Sabbath instead, buy that might not be economical at all compared to having even two Kohen Gadols for safety. Two Kohens has 10 RP total compared to 7 of a Kohen Gadol (with Magic-1).