Why did SE decide to make the three new classes not require base classes?

[Slick]

I don't necessarily mind the fact that they're getting rid of classes as the story for those jobs will now just be continuous rather than split into 1/2 Class 1/2 Job as it is now. However I am worried about what this means for the existing classes who are still bound by the system compared to their new counterparts.

You can't cross-class job abilities as it stands, none of them. You can only cross class "Class" abilities, so how will this work with the new jobs? Will they just be self contained and be unable to take or give anything from the existing classes? Or will they re-work this system entirely?

This is a very interesting question. I wonder if anyone here knows?