As a fresh new PC player who's in mainly for the immersion (rather than the combat, etc...), once the bugs are fixed enough i'd like very much an expansion on interactivity of the world and things that enhance immersion, so yeah : Animations for mundane things like buying and eating food, a really simulated subway system, being able to sit on many chairs and benches, more intractable food/drink street vendors, more connected things to interract with like lamp posts and traffic lights, alternative homes to buy, ability to display inventory content (like vinyls) in some places of the appartment... and maybe a little procedurally generated fedex quests, because I like to pretend I'm just a delivery man. Of course, many of the things I'd like are futile or unlikely, its just that night city is simply put the best environment I've ever seen, I'd rather have CDPR expand this marvelous world to make it interesting outside of main quest and side quests, rather than just make us wait 10 more years for a sequel.
Edit : Oh I forgot : I just tested the game in VR with VorpX. This is the best VR experience ever, even with all the bugs and clunkyness etc..., the feeling when you are just walking in the street with all the npcs circulating around you is priceless. So a proper VR mode would be fantastic, and VorpX proves it can be done and be good.