I have a feeling CDPR will address a lot of the technical/gameplay items people seem to universally be critical of, but some thoughts that would increase immersion and make the world feel more alive:
Repeatable mini-games from missions. This would be a fun way to pass time, and make some of the more unique mission encounters a bit more contextually relevant. For example: If I want to go to the shooting range any time, I should be able to.
Infrequent random encounters within Night City involving characters friendly to V. Could be as simple as seeing their car in traffic, or them going "Hey, V, how's it goin'?!" as they walk by. We don't have to go bowling with our cousin

would just like to see the AI companion characters not essentially be static in the game world.
Spawn police AWAY from the player when player gains wanted status without police present. If the game's lore is correct, and 7,103 people were murdered in the city in 2076, and the police response time is under 3 seconds like it is now...how is that possible? Police could spawn a distance away (long enough to seem like an officer was called from nearby) and then travel to the player, either on foot or by vehicle, or both.
Police patrolling the city, not just statically placed for encounters. In highly-secure areas, police and security forces could be seen walking the streets. In traffic, the various vehicle types could be seen on patrol. In more dangerous areas, less police. In less dangerous areas, more police. This, or some similar sensible method of reflecting the threat level in each part of the city. These police officers can respond to the player/NPCs if crimes are committed.
Emergency service vehicles should be seen in traffic (even if infrequently). Night City is intended to be a living, breathing city. While it makes sense to have Trauma Team respond within minutes to a paying customer, perhaps the city should have ambulances and fire apparatus to respond to emergencies, even if they don't actually do so in-game (parked near hospitals/fire stations, for example, or accompanying some police response events where someone is wounded/dead on the street).
Visible storage of vehicles and V's equipment. While I haven't 100% completed any playthrough yet, it seems as if the empty slots in V's cache never fill up with weapons, but V has an apartment, a weapons cache, and an elevator directly to the parking garage, all pretty much empty. The player could display vehicles and weapons in their respective places. These areas exist, make them useful.
Artifacts from the story should populate V's apartment, and the apartment should reflect V's life path/be customizable. Things that happen throughout the story could be reflected in V's apartment with memorable missions contributing something to the space. Also, V has three different life paths - being able to tailor the apartment to each would be a great way to make that choice more meaningful. the Nomad apartment has a lot more techy gear laying around, the Street Kid apartment is more punk/flashy, and the Corpo apartment is more refined and sterile, for example.
Some storefronts could close at appropriate times of day. As is typical for other RPGs, some shops in Night City would close at night (for example, the gun shop in Megabuilding H10, as the building feels a lot more deserted at night despite it not really being the case), and the storefronts themselves should reflect this. The day/night cycle currently is only cosmetic outside the number of pedestrians and level of traffic on the street. A simple change like this could help make it more meaningful.
Mass transit should be accessible and functional. Night City is, again, a living and breathing place in the context of the game. The game telegraphs that the city has working transit by having people go in and out of the subway stations, and monorail trains moving overhead. Restore access to the subway and elevated rail systems. There is also a bus in the game, though it doesn't spawn in traffic. Conveniently, it's drone-operated, so having it spawn in traffic at/around bus stops within and outside the city, or perhaps appear/drive off before/after fast traveling would make the city seem more alive.
Taxi services outside of side-missions. There are cars in the game painted to look like taxis, but not marked for the purpose and not functioning as such. It's also strange that Delamain's cabs only appear in their respective missions. Having taxis present in the city is a staple of the urban experience, and they could be spawned in traffic. Maybe V can hail a taxi to use for fast travel, as well.
Car customization. The current system of being offered vehicles to buy and being gifted them is actually pretty cool, but being able to tailor your own ultimate ride would be awesome. As in real life, making car customization costly would keep the current gameplay loops for acquiring cars relevant, but being able to take your car to a garage and customize it, for a few pretty ennies, would be awesome.
Vehicle variety. With 29 vehicles in the game, and a surprisingly diverse amount of variants each, there are plenty of cars on the road, but it's odd that in a lot of cases, there's only one type of each archetypal vehicle. For example, the Thorton Mackinaw (Michigan represent!!) is the only full-size pickup. Consider adding additional vehicles as free updates, as well as with the DLCs, to flesh out the variety of vehicles. Don't forget mundane/utility vehicles, too. We need futuristic station wagons, box vans, and pizza delivery vehicles, too

The cars in this game are honestly some of the coolest in any game, and they're all awesome. More of them, please! The Mahir Supron is mislabeled in the game and guide as the Makigai Supron though. Might want to fix that.
Clothing and gear - more variety/availability. Style is everything in Night City, and so far, the NPCs have quite a lot of kickass gear to wear, but the player is forced to scrounge limited inventory in shops and looting, with nothing really matching. It's hard for the player to express the intent for their character. Plus, all the NPCs get the really cool stuff! If more of this were available to the player, and the player could upgrade/modify gear accordingly, to keep the look they want, it would seriously make a huge difference.
Cyberware and character customization post-menu screens. Give the player the ability to change V's visual appearance outside of the creation menu, including "tech hair" and new "RealSkinn" options, like NPCs have. Also, make the body type/feature sizes that players select meaningful by having those changes reflected in the character model (chest size for female V, for example, should be indicated in V's outfits...not some weird request, honestly, just realistic and reflecting meaningful choices in the creation process...otherwise, why bother giving the option?).
I'm honestly loving what I've played so far...just hoping we get more, and that the experience grows to be deeper over time.