It's absolutely fine for some pieces of gear to be designed exclusively for one particular gender. Given the abundance of gear designed exclusively for female characters it is completely fair for something like Aymeric's armour to be limited to male characters - and before people bring out the usual 'they should make the female gear gender neutral as well' argument, I'd point out that that doesn't do a whole lot to appease those of us who play male characters and are perfectly fine with having some gear designed to fit a male character first and foremost.

A lot the 'unisex' gear and hairstyles are quite blatantly designed in a feminine or androgynous manner. This is very evident with a lot of caster gear sets and some of the hairstyles. When gear is more neutral in appearance or is designed with a specific gender in mind, however, it is typically allowed to have more depth to it. I'd point to the Songbird attire as an excellent example of this. We received two sets, one for male characters and another for female characters. I'd like to see more of that moving forward since it's an excellent compromise. The equivalent of Aymeric's set, for female characters, is Minfilia's attire.