1 - Start as Byzantium, true heir to the Roman Empire [Roman: 1/2]
2 - Go Catholic
3 - Become the Emperor, acquiring the Legacy of Charlemagne, and the Western Empire [Empire: 1/2]
4 - Renovatio Imperii, breaking with the concept of federalism and introducing the dominate once again [Empire: 2/2]
5 - Change government type from empire to theocracy
6 - Cause the downfall of the Papacy, and become the Pope [Holy : 1/2]
7 - Move your capital to Rome, the eternal city, conquering it if necessary. While you are at it, conquer every single province the original Empire (as well as Byzantine successor state) ever had [Roman: 2/2]
8 - Form the Kingdom of God! [Holy: 2/2]
Now you are twice-fold holy, as the papacy and Kingdom of God, totally Roman, as Byzantine emulating the original empire's greatness and having the capital in Rome and a double Emperor - uniting the generally hereditary Eastern Empire and the generally elective Western one.
As a further bonus you have grayed out, and thus harnessed the power, of the two main political entities in Europe.
And to make it even more epic - write it in a way so it is at least remotely plausible