IF the BLU/Sam thing happened, I think it would just be a Blue Mage and his weapon of choice just happen to be a Katana, and Artifact armor look samurai-ish.

I may had missed it throughout the long thread, but the biggest issue with BLU to me seems to be the weapon of choice. In this game, two jobs cant share the same type of weapon (SCH aside, but that's one root class.) What would be the Blue Mage weapon of choice in this game? If I recall correctly, in XI their artifact weapon (not only possible weapon) was a 1 handed sword.

If we speculate Blue Mage, we got to speculate about the unique weapon it would wield.