[quote=@The Silver Paladin]
King David vs Jesus, 
Ancestor vs Descendant
Problem: what class would Jesus be? He only qualifies for Avenger and Saver.
[/quote]

True, but Saver was considered an official class in Fate/Extra, so I don't see a problem (unless Fate/Extra isn't legit?). That said, Jesus' omnipotency would probably cause him to become a game-breaker like Gilgamesh, unless we're talking about the demigod Jesus chronicled in the Gospels.