I have my doubts that a former ruler would get so far as the curia, much less actually become Pope. I know of a few that abdicated and retired to a monastery, but that's about it.
Kings of Spain (Castile, Leon, Aragon, Sicily, etc.):
1516 - 1538: John III 'the Fortunate" (House of Trastámara)[1]
1538 - 1550: Charles I "the Blond" (House of Trastámara)[2]
1550 - 1552: Charles II "the Sickly" (House of Trastámara) [3]
1552 - 1565: Henry V "the Red Viper" (House of...
Kings of Spain (Castile, Leon, Aragon, Sicily, etc.):
1516 - 1538: John III 'the Fortunate" (House of Trastámara)[1]
1538 - 1550: Charles I "the Blond" (House of Trastámara)[2]
1550 - 1552: Charles II "the Sickly" (House of Trastámara) [3]
1552 - 1565: Henry V "the Red Viper" (House of...
Emperor of Byzantium
685 AD - 731 AD: Justinian II (Herclian Dynasty) [1]
731 AD - 744 AD: Constantine V (Herclian Dynasty) [2]
Emperor of Byzantium and Khazars
744 AD - 767 AD: Constantine V (Herclian Dynasty) [2]
767 AD - 789 AD: Constantine VI (Herclian Dynasty) [3]
789 AD - 829 AD...
Like any other 'ideal' form of government, this theoretical platonic republic would almost certainly end up failing to deliver on its promise of utopia. I'd have to go reread my copy to give you more detailed analysis of the specific ways it will fail.
What if William Stanley, 6th Earl of Derby (whose maternal great-great grandparents were Henry VII of England and Elizabeth of York via their daughter, Mary Tudor) becomes king of England?
Kings and Queens of England
1558 - 1603: Elizabeth I (House of Tudor)
1603 - 1642: William III (House...
Kings of England
1135 - 1160: William III (House of Normandy) [1]
1160 - 1182: Henry II (House of Normandy) [2]
1182 - 1188: Henry III (House of Normandy) [3]
Kings of England, Princes of Kiev
1188 - 1245: Sophia (House of Kiev) [4]
1245 - 1259: Gleb (House of Kiev) [5]
1259 -...
Kings of England
1135 - 1160: William III (House of Normandy) [1]
1160 - 1182: Henry II (House of Normandy) [2]
1182 - 1188: Henry III (House of Normandy) [3]
Kings of England, Princes of Kiev
1188 - 1245: Sophia I (House of Kiev) [4]
1245 - 1259: Gleb I (House of Kiev) [5]
1259 - 1277...
Kings of England
1135 - 1160: William III (House of Normandy) [1]
1160 - 1182: Henry II (House of Normandy) [2]
1182 - 1188: Henry III (House of Normandy) [3]
Kings of England, Princes of Kiev
1188 - 1245: Sophia I (House of Kiev) [4]
1245 - 1259: Gleb I (House of Kiev) [5]
1259 - 1277...
Kings of England
1135 - 1160: William III (House of Normandy) [1]
1160 - 1182: Henry II (House of Normandy) [2]
1182 - 1188: Henry III (House of Normandy) [3]
Kings of England, Princes of Kiev
1188 - 1245: Sophia I (House of Kiev) [4]
1245 - 1259: Gleb I (House of Kiev) [5]
1259 - 1277...
Kings of England
1135 - 1160: William III (House of Normandy) [1]
1160 - 1182: Henry II (House of Normandy) [2]
1182 - 1188: Henry III (House of Normandy) [3]
Kings of England, Princes of Kiev
1188 - 1245: Sophia I (House of Kiev) [4]
1245 - 1259: Gleb I (House of Kiev) [5]
1259 -...