I disagree with the thought of classes being made to be weaker than jobs intentionally. The team was rushed, had very little to work with, and way too many client limitations. Jobs were introduced with their names as they are mainly because people wanted that nostalgia. There is nothing wrong with classes being separate entities. One limitation being the ability to even add more classes, or new things to level up. Which I feel is why we have class-job locking in the first place. I was always against not having to level up the job separately from lvl 1 after you unlock it. With ARR's lack of or reduced limitations on what they can do, they can make things right.
The idea of More than one job branching off of current classes only means there will be little to nothing to level up in coming expansions, and in order for it to not be broken and/or stupid, they would have to overhaul every class to preform different skills than jobs anyways, or else every job is going to be the same thing with different names if it comes from the same class. Such as DRK also coming from GLD will be a take UNLESS they overhaul glad to not be an extreme tank by itself, but only change to extreme tank if you are on PLD, and be something else if you are on DRK. But then they would have to follow my above example anyways in order to achieve that. The class would have to be different than the job. The Idea of branching more than one job from each class also ensures that there will be little to nothing to level up once a new job is announced. I for one do not want to be instanta lvl50 at expansion time, and don't even have to play that new job in order to lvl cap it.
There also no reason to assume that classes cant or shouldn't take on party roles. Class and job are just names. We call WHM, WAR, and the others JOBS because other FF titles they were part of a JOB system, and after the class reforms, classes took on party roles WITHOUT the presence of jobs. But remember that none of those other titles had more than one CLASS beyond squire if you would call that a class or 'that player'. It was always one thing until they got a job crystal or lvled up enough to become a different job. FFXIV's classes could be made to have roles of their own, however their roles should not be Identical to the jobs that branch off of them.
So if you look at it from a logical perspective, there are no jobs in FFXIV, only classes and advanced classes. With a reform to separate the class from job, there will no longer be 8 classes and 8 advanced classes, but 16 classes to use in a party. Each and every one could be balanced to be able to solo, as they all already are, but not be the same like they are now, and still have their own roles in Parties and raids.
This is not about going back to being able to cross class every ability and be a god. This is about helping classes have more usability besides these rare solo cases. Yes overhauls take time. Unfortunantly they will inevitably have to overhaul classes and jobs multiple times as they add new classes, new jobs, and new content. Especialy if they plan to branch more than one job off of one class. Overhauling will be needed. Else, what can the next JOB to branch off of THM be but another BLM without the ancient magic that uses the exact same weaponry? Ancient magic is not what makes the BLM, its all the other fire/ice/lightning/other elemental magic - which is learned by the THM under this poor system, not the BLM - that makes the BLM.