Q: Both of the races have characteristic head designs. What will happen to headgear?

Yoshida: It won’t be displayed. It’s impossible with the current FFXIV’s system because of Viera’s and Hrothgar’s faces. The logic is that it was impossible to make helmets that would fit. For example, if we talk about Viera’s ears, you can make them fall sideways in which case we have to make the be in the same position as Miqo’te’s, otherwise it wouldn’t resonate with the system. So, we thought that if we don’t make new races that have new looks, that it doesn’t make any sense to add any, so I decided that it doesn’t matter if they can’t wear helmets. Therefore, no matter what helmet you equip, you can equip it, but it won’t graphically show. However, we did decide to enable display of head pieces that hide the entire head, so if you want to wear the Fat Chocobo Head, you can. Glasses and Circlets won’t be displayed. If we were to separately decide which item is fine and which isn’t, we would have to go through a huge number of items, so we decided to disable the graphics completely and only allow the headpieces that hide the entire head.
I've come to realize that Yoshida is a professional liar. Either that or he lets his coders feed him heaps of BS and is showing incompetence at his own duties.

So with the Viera, there are things that hide just the ears. Which means they could use the same API call that does that and apply it to helmets, solving the issue for Viera. Their heads and faces are not oddly shaped. And this isn't the only thing the producer has said that is outright false. Pretty much anytime he says 'system limitation' he's lying out his ass.

What is really happening here is some coder can't be arsed and either Yoshida doesn't want to bother them, or is believing there is 'system limitations' when they simply are too lazy to run through the database. Its pretty bad when modders can get around such 'system limitations' in other games. I'd wager some of the modders in this game could do it too.