Morgan can already inherit weirder classes(Fighter, Villager), so why not Conqureror if his father is Walhart. Overlord's max stats aren't obviously overpowered like alot of boss classes and its not like Awakening's classes are that balanced anyway.
Before anyone mentions this would give Female Avatar/Male Morgan an advantage over Male Avatar/Female Morgan, note that Manakete is only available to female Morgan as there are only female Manaketes in this game for some reason.... So it would work out evenly.