In 1453, Mehemd II, the Ottoman Emperor, delivered a ultimatum to Constantine XI. It stated that if Constantine XI gave him control of Constantinople, he could contine to rule in Morea, otherwise he would lose both. IOTL Constaine XI rejects this. However the POD for this TL will be him accepting it and moving to Morea.
How long could his rule last in Morea? Would it become a ottoman vassal state? Would the ottomans just stab him in the back and take Morea almost as soon as he arrives? Could the Hexamillion wall across the Isthmus of Corinth be repaired and made into a formidable defense against the ottomans? Could the byzantines also achive naval supremecy to make the wall effective? Where would the new capital be?