So, there's a few things that come to mind when it comes to the topic of adjusting or adding to retainer functionality.
**Hairstyles**
So I'm sure that most of us are aware that we can obtain additional hairstyles than what's initially available through character creation. I don't know whether retainers not being able to display unlockable hairstyles is an oversight, a technical limitation, or a conscious design decision. Being able to do so, however, would be nice quality of life option to have available for our companions, who are often on display at our cottages, houses, and mansions.
**Companions**
Speaking of companions, I think this feature is long overdue for an update. As of now, players can call forth their chocobos using Gyashal Greens. I propose that the the functionality be extended to, and further expanded upon, for retainers. Retainers are already capable of leveling up and equipping gear. Having them play a more active role in our adventures makes those changes more visible and presents several possibilities. Roleplayers in need of traveling companions would be able to create new narratives. Players who level multiple jobs can have their hard work reflected in their retainers who can play supporting roles that synergize with a player's active job. Having retainers on full display also presents a monetary incentive via the Mogstation. For example, a male character with little incentive to purchase the Scion Healer Boots may be more inclined to do so if he happens to be accompanied by a female retainer.
**Dungeons**
Being able to take retainers to dungeons further expands on the concept of having them more present alongside the player character. I would imagine that a feature like this would function similarly to how squadron dungeons are implemented into the game already. Being able to take multiple retainers to a dungeon could also serve as an incentive to purchase additional retainers via the Mogstation. While we're at it, why not take this idea a step further? Trials tailored to retainers and squadron units presents an entirely new form of solo content. Players can experiment with party compositions and coordinate strategies against bosses by taking on a sort of a team manager role. Deep Dungeon runs could also gain an added layer of complexity and player choice.
I know that asking for the implementations of features like these is a tall order, especially given that they fall outside the realm of what most players consider as "core content". But I encourage those reading this thread to at least consider what this extracurricular content could do for players looking for more outlets to express their passion for the game-- and how enabling these players to do so could see potential returns both creative and monetary.