What if the Exo are a similar project as GLaDOS? During the golden age maybe the humans searched for a way to make ourselves less "weak" to some space environment/enemies. Though putting the mind of man in a machine have its own risk. So maybe it is a machine with a soul, thus telling why the Ghost (traveler) choosed to bring them back and give them magical powers, because if they were simple robot they would not be "mysterious". Human already have "normal" robots in the city so what makes the exo so "special"? Note: The creator decided to give them Male & female representation.