GLA doesn't have to be noble, and holy like a PLD does. GLA has it's own story just as much as PLD does. Theoretically the mechanic in the game requires GLA at a certain to become a PLD if the player chooses to, so with that in mind remember that GLA has to stand on it's own in terms of lore.
It's not hard to put together a quest-line involving the "money-making-entertainer" who chooses to follow the path of a holy knight. We shouldn't have to expect the reworking of the original classes to have an understanding of the advanced jobs.
