As much as I loved BST in FFXI, I don't think they'll be doing that here. With the whole feral souls thing been featured not only in the DT MSQ but also an integral part to the new Raids, I can see the devs going down that route.

It'll basically be Blue Mage but with different animations, different weapon and saying it's an ability rather than a spell.

As for the whole "It comes from a shard" - they'll probably make it start at level 90 and require you to go to Alexandria to unlock it.

I really hope I'm wrong and it does turn out to be a proper BST (like FFXI and other games) with a newly designed pet AI system the devs want to try out to use on other jobs in the future job rework, but then again I though Island Sanctuary (when announced) may be the precursor to instanced housing . . .