I'd be sad to see the classes go to be honest. I really like the class stories and trainers and would rather not see them removed from the game.
I also like the idea of your character starting as a class when they're a newbie adventurer then becoming a job as they grow into the Warrior of Light.

I have no problem with new jobs having no starting class or doing something like making the transition to the ARR jobs easier by removing the requirement to level another class. I could also see SE making the transition mandatory by capping classes at 30. I would just be sad to see the class stories disappear entirely.