I believe the apartments are due for a revisit from the dev team. Although housing is incredible, I believe apartments can be very comparable to housing. Currently, apartments are only missing a few things that could be remedied very quick with a few adjustments.
Here are my suggestions, please add more below!
1. Add an instanced "outdoor" porch:
This to me is possibly the biggest feature that could help players feel they're not missing out on not owning a home, but also not taking away from those that do. A small porch / outdoor area where people can decorate with outdoor furnishing would add more value to the seasonal events and foster good will with players. It wouldn't be as big as the small house yard, but it would at least give players an option.
2. Increase the floorspace (not the floors):
Currently the floorsize of an apartment is not terrible, but could be increased. I could be wrong, but it seems smaller than the basement of small houses. I think it should be increased to the size of the basement of small houses. This would be a great quality of life change for apartments and still preserve the special feeling of small/med/large houses of having mult floors.
3. Increase the item space:
Personally, all houses should have an increase item size of at least 50-100. Again, this would allow players more options and higher value all the furnishings added to the game.
4. Provide an option to upgrade apartments to multiple floors in the future:
This is a shot in the dark, but maybe the apartments could be provided with upgrade feature to increase the floors to a small/med/large (penthouse!). Although the outdoor space would stay the same or increase only slightly (still keeping value to the houses), this would provide so many players with the fun of having a home without the disappointment of the very limited current housing system!
Apartments are such an incredible feature in this game. They provide a lot more to the general health of FFXIV than I think many people may know. Apartments are a great way to keep the economy healthy, since they further player investment even with those that have houses. Apartments also allow players to enjoy all of the housing districts without taking houses away from other players. Apartments also provide a horizontal progression for players outside of the gear chase, and increases the lifespan of many players' subscription. All of these points are great for SE's business! Please consider these suggestions and revisiting apartments dev team!