1. A return to the expansive, ARR -style, map design;
Noticed this trend since ShB, the map design is clearly geared towards "higher" level players and suited for efficiency like an FPS type of map rather than a living, breathing, place that you can explore. ARR and HW had irregular maps with many small details that rewarded exploration and keen eyes; all of the Gridania zones, the chained frozen dragon in Coerthas Western Highlands, etc. Zones since ShB have become more "boxed in" and homogenous in design elements with little attention to mob placement or design. EW maps feel very "artificial" and much smaller than previous expansion zones. I can understand the lore for most of zones in EW would lend them to being "artificial" but you can't say that Thavnair isn't criminally under-sized. If Thavnair was made during ARR era, it'd be much bigger and more varied.
2. Increase in mob models/ unique mob design
I get that its industry practice to reuse as many assets as possible but it's a bit much how much things are recycled with little change. You can take most of the blasphemies and put them in a dungeon from ARR, HW, SB, or ShB and they wouldn't stick out at all. I get that they are supposed to be lore-inspired from each region but surely twisted, aberrations would look much more different than a dragon or behemoth model but in different colors. The asset reuse gets to be an issue when it butts heads with the lore; people starting to question why the transformations look eerily similar to voidsent. It is starting to be immersion-breaking whenever I see a new boss monster and I think "huh thats the 3rd time they used this skeleton".
3. More facial/overall character customization
I don't expect going anywhere near BDO-levels of customization anytime soon but you get a lineup of 10 player characters of any race and they would all look very similar. I think players should be able to easily create unique looks that distinguish them from generic NPCs without having to resort to looking like clowns. They could even go the lazy route and take pieces of various racial features like eyes, noses, mouths, and let them be used by different races i.e. Viera eyes/mouths be used by Hyur, etc. This would double customization options with minimal effort of having to come up with totally new features. Its obvious that the base customization tool is lacking when they needed to make unique facial models for lore important NPCs like Hien, Gosetsu, Foruchenalt, etc instead of using their own ingame tools.
All of these base-level problems should really be addressed in 7.0. If we are gonna be visiting distant lands, shards, or planets in 7.0, it'd be underwhelming to see the same-looking mobs and NPCs from Eorzea that we've known for the past decade. I'd love for the next arc to start off with a whole fresh coat of paint and some sort of modernization.