This would be a nightmare to code. There would need to be a separate slot for "face" and "head," of which there isn't currently. And adding new item slots is something you have as a feature in a new expansion.
Sooo even if they DID decide to do it, it's years away. And they probably won't because it would mean reworking nearly every single item in the game. Especially ones like the BLM AF gear that is both a hat AND an eyepatch.