I was extremely disappointed when I heard about the specialization system. As the name suggests, this system most likely will be exclusive in nature. It's like saying each character could only specialize on a few battle jobs and the rest will not be able to do end-game content.
In my opinion Yoshi-P is throwing away the biggest strength of the FF14 design, where one character can do everything the player wants. It's already started with the desynthesis system, and specializations is just going to make the whole crafting system exclusive like any other MMORPG out there with a mediocre crafting system.
Seriously, please, Yoshida-san, don't deviate any further from the core attraction of FF14---being able to do anything by just changing the main-hand equipment. Specializations are great if the game was designed to be exclusive. But FF14 is based on an inclusive concept.
Put your "specialization" system on top of the battle jobs and see if it makes sense, please.
On the other hand, if it turns out that specialization is inclusive, i.e. one character can obtain all specializations and be able to use all of them at the same time, then sure, why not.