While that city might be taking it to the extremes, I wouldn't mind cities to be more sprawling and integrated. I understand that they need the district info to be "at a glance", and while I'm not sure people really use it that much, it's a sympathetic thought. But maybe there could be a bit more "filling in the gaps" to make city look more coherent.
Unfortunately, once they went with discrete, separate Districts, any graphic coherence in the cities disappeared, and ain't likely to come back without modification of the entire District system.
Like, Districts should be modifiable and even convertible: as mentioned above, Classical, Medieval, Renaissance Era cities didn't really have separate 'Industrial Districts' at all , unless you counted the area by the river where all the water wheels went by the mid-Medieval period. Workshops were scattered throughout the city, usually in separate 'streets' that specialized in one type of manufacture (there were, for instance, a Street of Sculptors and portrait artists and a Street of Armorers in Classical Athens, and the members of Guilds tended to 'cluster' in Medieval cities). The buildings in 'Holy Sites' - temples, cathedrals, mosques, etc. were almost always found in the middle of the city, not out in a separate district in the countryside. Neighborhoods were built up separately only when stea-powere transportation in the 19th century (Industrial Era) allowed people to travel into the city easily. In the Atomic Era and later, the trend has been to convert older Commercial, Port, Industrial areas into Neighborhoods - "Gentrification". All over Europe Renaissance Walls were torn down in the Industrial and Modern Eras and replaced by 'ring roads' - "Boulevards" in the original sense - and now many of those include green belts and mass transit lines.
So, aside from 'simple' graphic changes like giving us a variety of potential 'modern' city styles instead of every city becoming Shanghai Steel Sick-Inducing, I'd like to see some major revisions of the Districts to better reflect the 'real' growth and specialization of cities - and their defenses. It is, IMHO, ridiculous that the only part of a city that can be walled, even in the Classical Era, is the city center and 'encampment' - which has to be separated from the city center, making the defenses separate as well. Every military and civil engineer in the world before Prussia's 'detached forts' of the mid-18th century would be spinning in his grave like a top!
Here's a sample set of changes:
1. All Districts before Steam Tech must be adjacent to the City Center or to another District that is adjacent to the City Center. That, of course, would require modifying the entire 'Adjacency' system, because you won't have the freedom to scatter your city in detached districts all over the landscape as we do now to 'maximize' Adjacencies until your population can actually travel back and forth easily between them.
2. The City Center should be much more flexible. Specifically, there should be the option to build a Shrine/Worship center there in addition to or as part of the Monument. This wouldn't be as efficient or powerful in its influence as a separate Holy Quarter with a Temple (higher level 'worship' structure), and the Holy Quarter should get a major boost if certain Wonders are built next to it - namely, any 'religious' Wonder like Hagia Sophia or St Basil's Cathedral.
Another point is that Civ-Specific graphics can be added for the 'central worship structure' and the Monument, and some Civs would combine the two in one structure: an Aztec Pyramid with sacrificial altar on top, for instance, or a Greek Agora combining a Stoa and Shrine - there are lots of examples that only require a non-animated graphic and a change in numerical factors, if appropriate.
3. All Districts are convertible to some degree. Ones that I have seen personally in (Atomic Era) cities from the USA to Germany are:
Encampment to Neighborhood (Aschaffenburg, Berlin, San Francisco's Prasedio district)
Harbor or Industrial Zone to add Neighborhood features ("gentrification")
Holy Site to add Commercial Hub features (York Minster, the
Domplatz in Mainz)
Encampment to Park
The requirements would have to be carefully defined, and usually involve later Eras, especially when the size of cities changed dramatically in the Industrial and Modern Eras.
4. City defenses would cover the entire city including its contiguous districts, and adding later Districts would require also 'extending' the Walls to cover them. Before the Industrial Era, when city walls essentially became obsolete, this would require more expense (or another 'use' for Military Engineers). On the other hand, walls now made obsolete because they cover a tile side now inside the city could provide Bonuses (see Rothenburg-ob-Tauber, a little Medieval city networked by 'internal' walls it outgrew, which are now some of the major tourist attractions in the town, or Paris, Vienna, or Berlin, all of which outgrew their Renaissance Walls, tore them down, built major Ring Roads/Boulevards on the sites around the city)