Actually, the Holy Roman Emperors of the Saxon and Salian had the right to nominate the pope, and Ottos (I, II, and III) intervened regularly and deposed popes not to their liking. It wasn't until Henry IV in the mid 11h century that the papacy challenged the emperor's right of nomination with In Nomine Domini that created the college of cardinals.
Granted, CK I begins in 1066 when this is already in place but I'd like to see CK II begin in late antiquity![]()
The features being discussed for CK2 would work well for as far back as the Carolingian period at least and as far forward as the late Renaissance (with some adjustments), so plenty of room for modding in late antiquity, my friend.