Seems to me quite a few of the jobs and classes in FFXIV are combinations of other jobs/classes through the series. If they added BST and incorporated Morpher elements into it, well, it doesn't seem to be much of a stretch to me. Or heck, they could add BLU and give it beast-based transformations ala Morpher.
Some classes/jobs may share spells/abilities that we saw previously on other classes/jobs, but the core identity of the class/job is still intact. There is no current example of one class/job completely inheriting the mechanics and identity of another class/job.

Regardless, we are just arguing semantics here.