Italy,Balkans,Anatolia,Parts of Eastern Caucasus,Most of Syria,Lebanon and Jordan and Egypt. This is the best case scenario for them to survie. Gaul,Hispania and others are left for Germanics to settle after they invade them. The capital is located in Greece region or is Rome itself. Considering it would be the former(Byzantium) establishing such an Empire,it would be in Greece. The majority of citizens are Greek as Italy and Northern Balkans are the only non Greek regions. Egypt,Levant and Mesopotamia are all heavily Hellenized.