Final Coil of Bahamut spoilers ahead:

The peoples of Eorzea already have a primal that they called upon on the brink of the calamity. It's Phoenix. That seat is already taken, you cannot be a primal called upon by the peoples of Eorzea.


(non-spoilerish version: Nopz, no chance you're a primal called by the peoples of Eorzea). Also, you've been around since before the calamity. Also, you're not the only one. Ysayle is revealed to be just the same as you just before her horrible death at the hands of the Garleans. Difference being she only had ONE crystal and thus didn't complete the blessing like you did by having all 6.