If Byzantium gets the possibility of owning Rome, then I'll surely play with them until I get all of the Roman Empire extension before UHV3. A dream coming true.
I remember my first (historical victory) successful attempts with them, my evolving timeline would be like this:
1st - All Anatolia, Greece and its isles, plus some vassals
2nd - All Anatolia, Greece, its isles, Macedonia and Bulgaria, plus some vassals
3rd - All Anatolia, Greece, its isles, Macedonia, Bulgaria, Serbia, Mid East, Egypt, Cyrenaica and Cyprus, plus some vassals
4th (Augustus Caesar Score Beta 13) - All Anatolia, Greece, its isles, Bulgaria, Hungary, Iugoslavia, Italy (except Rome of course), Sicily, Provence, Mid East, Cyprus, All North Africa (up to Gibraltar straight), Crimea and Kiev, no vassals
5th (first attempt at RFCE 1.0) - All Anatolia, Greece, its isles, Bulgaria, Iugoslavia (except Serbia), Italy (except Naples and Rome), Provence, Tolosa, Lyon, Catalonia, Aragon, Navarre, Andalusia, Mid East, Cyprus and All North Africa (up to Tetouan), one vassal.
When possible my aim will be:
All Anatolia, Greece, Hungary (except Upper Hungary), Austria, Iugoslavia, Italy, France, Saxony, Franconia, Flanders, All Iberia, Great Britain (except Scotland), Mid East, All North Africa and All Mediterranean Isles, max number of vassals.
The only thing that can stop me is winning by Domination before completing it. I hope that these plans to change the Papal States go on and allow the recreation of the Roman Empire.