While it would've been a nice option at launch, I think it's too late to go back and fix anything going forward.

They'd need to commission the work to re-record hours worth of dialogue, which would be awkward for the characters whose voices have been replaced in later parts of the game or whose voice actors have since deceased. There's the matter of having to re-code gear and dialogue options away from the binary and which words they'd use for miscellaneous gendered words like lord/lady or master/mistress. And then there would be the question of how to handle this in the 3 other languages because German, French, and to a different extent Japanese lack proper gender neutral pronouns.

For the bodies, the game is barely held together by ARR-era server coding that boils our characters down into specific options that already seem to be at their limit of what the system can handle, which is why if your race has an ear/tail slider, it won't have a muscle slider. We can barely get 2 new full races that can't even wear hats so I don't believe the devs have it in them to add non-binary gender information in for everything else.

Ultimately while it's something important to be aware of for any potential future game and I personally know people who would be interested in it, I think that ship has long since sailed for FFXIV and the amount of resources required to overhaul what exists most likely doesn't outweigh the interest and motivation of the dev team to do so.