I’m sure these have already been suggested to some degree, but I think that given the great amount of detail and effort put into the roleplay and feel of the game, with food, cafes and the whole backstory, there are some key features that might heavily improve the game’s aesthetic.
First and foremost character personalisation, (clothing) being able to see YOU, wear different clothes, your beige detective overcoat, hat, etc would just help with the immersion.
Different clothes could provide different buffs, and clothing could be a great way for players to have an extra goal, as clothes will not only allow them to look how they want, but also provide benefits. (Unlike buying a bigger apartment that does nothing really)
Secondly, smoking. There is pipe tobacco, pipes, cigars, lighters and cigarettes, but no way for you, or any other npc to smoke.
It would be cool to see NPC’s going around with a lit cigarette in their mouth, leaning against a wall while smoking their pipe etc.
Finally, some extra noir soundtracks, or sound effects could be added.
Depending on the situation, like if you’re trespassing (sneaking in) or being chased