That being said, if SE is wanting to bring the traditional Final Fantasy jobs into the game, they'd have to scrap the old ones.
They don't really. Either the traditional classes specialize from the current classes or they are advanced classes you can branch off to after leveling the current classes. The lore is already in place, as well as several quests fleshing out the classes, so it would not make sense to 'scrap' them. Their backgrounds are unique enough to allow for them to be even part of the specializations if they wanted to do it that way. All they would need to do is make their equipment and abilities stand out (Gladiator to gain "Hercules's Fury", "Zeus's Wrath" and "Caesar's Perseverance" skills for example).
What I was getting at is the idea that our current classes are just combinations of traditional classes. They've just been butchered up and stitched back together.
That being said, if they added... say, Paladin. Gladiator/Sentinel is already in the game, and already has abilities that are unique to Paladins, such as Cover. It wouldn't help the game to have two classes that function in similar manners. We already have more than enough of that. So if they added a Traditional Paladin, they would have to give it Traditional Paladin Skills. But because Gladiator already has some of those skills, it would be redundant to let Gladiators still have them.
The same could be said about the other classes and their traditional variants... Pugilist and Monks... Lancer and Dragoons... To be honest, the only one that comes close to being their traditional counterpart is Archer. But even then, Rangers could still equip melee weapons and guns....
I know there have been a number of posts about wanting to make a talent-tree system, and dress it up like a License Board. But that defeats the purpose behind switching classes around. One of the great things about FFXI, (suck it up, I'm comparing them), is that players could change their jobs very easily. That was one of the major traits that worked out very well for the game. SE even intended that feature even more accessible in this game with the Armory system. Taking into consideration that the Stat/ Action Point Allotment system, (for as absolutely terrible as it was executed), was intended to let players change their play-style quickly and easily. (Though this is not the actual case, that was the intent. I'm sure most of us can recognize that). This said, talent trees are not a good way to implement traditional classes.
That leaves us the option of making the traditional classes actual playable classes, and not specs, or hierarchies. If they implemented the traditional classes, they will have to either take away the original FFXIV classes all together, or revamp their abilities so that they don't over-lap with the traditional classes. Example: A Gladiator is LFG next to a Paladin. The Paladin is the obvious choice, and would completely remove the need for a Gladiator.
Or, there is the horrible nightmare idea that SE could ***** up even the traditional classes, leaving the original FFXIV system more desirable. Example: Who wants to level a Black Mage, and be stuck LFG against all the other unique DD-onry people, when they can play a Conjurer and heal/buff themselves, while having access to Ancient Magic? (Though AM sucks right now).
Granted, that goes against the spirit of MMOs, but there will always be noobs who don't care, and just want to be omni-powerful, with an audience.
So yes... If they're going to add a real Dragoon, they might as well get rid of Lancer, cause no one is going to play it.