**Spoilers ahead if you haven't reached this city yet**
It feels like this expansion should've focused much more on Everkeep and its tower levels. Tuliyollal could've been a way to shake the tired old mold and made it the smaller city that you go to first. Wuk's subplot could've been vastly cut down without much issue and kept focus on what was the point, WoL going on their own adventure in a new land.
I won't touch on that much more than this, as my main focus is the vast amount of detail that went into Solution 9 that will likely be left dormant given SE's track record. The city we see is only a sliver it seems of the level of as a whole, yet within it a lot of aspects could've been added for the fun of it; I wanted to share my thoughts on it.
Air-wheeler content
The city is set up with an Air-wheeler Dealer, Mod shop, and freeway/highways; there really isn't any better shoe-in for a mini-game than this. It could be SE's redemption at abandoning Choco Racing yet still be plenty different in its own regard. Either races that differ based on your mods, that can lead to tournaments or FF7 style survival chases that require different loadouts; adding content wouldn't be too hard. Keeping things relevant can be done with just adding new rewards from time to time, updates don't always have to be massive to side content.
Fortune Teller content
Something small but fun to do maybe once a day if you want. Go get your fortune read and varying results depending on any number things: choices of questions, chance of cards, weather forecasted, maybe add a component from AST. Fortunes obtained could be a range of things, can even be specific on certain days like '+20% EXP from Fates in X Zone'; a way to get people to gather in the world proper etc.
Drink Vending machines
Could have a set list of drinks that do specific things, funny fluff stuff that is similar to the glow you get from the MSQ. Also could have a mystery button that drops out both common and rare things, to keep things interesting.
Luxury Apartments
The entire set up, aside from the housing code itself, is already there. Sol9 Apt's could be its own first ward of just that, apartments without houses. Give the ward a similar building as shown in the city, but a suitable size for being its own neighborhood. It would be a good first start to break the old mold of typical housing.
Neon Stein
Not to much to be said here except if it were made a bit larger, had a functional music choice/NPC that played a specific times it could've added another spot to hang around at. Maybe even add a sign up queue for bard groups to perform etc.
QoL of Sol9
More than a handful of times I've already seen people disappointed at no market board within Sol9. It has the potential to be a great hub hang out so adding this would be an easy and welcome addition.
All in all just my thoughts on the city that could've been more. Maybe there's stuff I missed, feel free to add your own thoughts.