And yet FFI didn't have PLD as a Job - it had 'Knight'.. as it's upgrade from WAR (or 'Fighter' as it was called in the original NES version). And what does the Knight sprite wear on it's head? A mask not a helm. And I don't count the WoL artwork used for FFI's logo as it is irrelevant to this arguement being that was Yoshitaka Amano's artwork (and thus came entirelly from his own imagination), and not representative of the actual game itself.

FFXIV takes it's cues for PLD from Cecil in FFIV, as I mentioned. And Cecil wears a coronet in his PLD form. Every other iteration of PLD in the series followed this lead. If you want to wear an enclosed helm for PLD glam, that's completely fine. You're just simply never going to see it included as the Job's AF, that's being realistic.