I'm totally for flexibility, but don't we already have the tools to do that? Can't you already equip the tools to do that?
We know that each job is going to be a set of skills in some form that you unlock via quests. In the case of white mage I imagine that would be higher tiers of Cure, Regen etc. Do you want that to be accessible to every job? How would that work? What kind of penalty would a Lancer face for advancing their currently non-existent healing skills? (because as we know, a specialisation placed on Lancer would mean they'd become focussed on White mage, not that they'd become LNC/WHM)
In addition to that, doesn't that just kill the whole 'specialisation' and also the return to classic final fantasy jobs that they're shooting for?
The alternative I can see (correct me if there's another) would be that EVERY class gets their own skills for EVERY job, which would be totally unrealistic.