Congratulations on over 100k units sold. I’ve been playing computer games for over 40 years now, this game is one with the greatest potential.
I deliberately don’t post this under feature suggestions (many users probably already used their votes?), but as a basis for discussion, maybe also on steam.
What I’m missing here with all the popular suggestions and ideas is the role-playing aspect. A bit of humor here and there wouldn’t hurt either, especially in an otherwise bone-dry tycoon game.
I know that it would be a lot of work, but with the success so far it is conceivable - but not in a year, because additional programmers would be needed (I guess).
An extended EA phase would also be my first suggestion. With all the listed content, it would become a million-seller despite the tycoon basis. Sorry if some ideas have already been posted, i didn’t have time to read them all, this game has already stolen 50h of my sparse time… 
Politics & Interactions
What is the greatest wealth worth if it cannot be translated into power? In real life politicians are often influenced by lobbyists, I think that’s a “must have” in this game.
As political offices, there could be trade and building supervision, the tax office, banking supervision, customs, environment, etc. in addition to the mayor - bribes could lead to advantages or disadvantages for future competition.
Applying for mayor yourself would certainly also be something that could refresh you in addition to the boring everyday life later in the game. To top it all off, getting elected for state elections all the way up to the presidency would be a great career opportunity.
Some people also call for a criminal underground, e.g. as a drug lord - if you are considering that (DLC?), you would already have the right foundation for it.
A judge or prosecutor as a bribe victim or even a playable role would also be great, including a privatized prison? Bring your competitors to your jail and torture them! (optional 18+ content…)
In general, it would be nice if there were some people in town to interact with, as a kind of quest system with various rewards or just for fun.
Competition and lobby groups
What ideas do you have regarding the competition planned for 0.3? Sabotage would be important (especially in multiplayer), could also be optional. Industry and other lobbies are worth considering, enough money could buy influence and power.
In any case, it would be boring if you could only buy up competitors and they hardly defend themselves - hence the idea of political offices, etc., which can also be filled by competitors.
Services
There is a hospital, but nothing more is planned? Medical practices, dentists and especially pharmacies would be important (at least more important than gift or flower shops).
I think enough has already been suggested here, e.g. delivery services. Call girls or call boys would be a funny idea and would loosen up the otherwise dry gameplay and provide humor (black screen when visiting) and a large mood buff.
Press and Social Reputation
Newspapers and media are very important and should not be missing. Again a potential candidate for your own company.
An in-game newspaper would be great and another avenue for advertising and manipulation.
Of course, prestige can also be bought, but unfortunately it is not included in your future plans? Might be divided into several areas: reputation among working class, middle and upper class, factions etc.
Factions
Whether it’s political or lobbying, I think factions would be important in general. Environmentalists, conservative capitalists, underground, moneyed gentry - there are many options here.
In any case, they should be dynamic and have an impact.
Church/Religion
Based on the same system as in politics. New service: Missionary Office (begging for money and converting people, maybe with a little humor). Founding your own religion would be hilarious.
City Life
There’s already a little something planned. Street musicians and other artists, beggars, thieves, children playing, animals - such details turn a good game into a great one.
I’m curious what to expect with the random events. Festivals, street parades, demos would be great.
Seasons, Weather, Fires
Yes, a very big chunk, not only for the graphic designers. It would also offer significantly more depth and possibilities:
Supply and demand depending on the season, slippery roads in winter, additional business opportunities (ice cream, winter clothing, etc.), appropriate music for the weather, heavy rain, storms, thunderstorms - it would increase the atmosphere of the game enormously.
Fires would also be appropriate, since there is no fire brigade (should have something to do if implemented) - also a nice opportunity for sabotage. Yes, just such a fire system is a lot of work… sigh.
City Expansion & Access to better areas
Before you tamper with London and Paris, would it be possible to expand New York? Would also be an interesting approach to only unlock the better city areas when you are far enough in the game.
It’s too easy to rent right in Midtown and make twice as much profit - in real life not every owner would rent to a random wannabe?
Banking System & Scoring
In story mode you could set it up so that your uncle acts as guarantor and therefore you get a loan, but as a penniless bum in freemode?
Several banks would not hurt here, e.g. one that gives small loans to ordinary workers. Would also be good for humor later on: advertising calls or emails from the bank trying to talk you into a loan.
Hopefully you plan to set up a stock exchange company yourself and trade in shares (also from the competition)?
Founding your own bank would of course also be useful as an office business.
Mail & Emails, Social Media/Scoring
We have phone calls in text form. There is a lot of potential here, would be an important system for some other suggestions and a great basis for some humor, everyone likes spam mails!
Postman and parcel delivery (why do I think of sabotage right away? Stink bombs?) included.
Social scoring would be great. I’m thinking of a platform like “Twidda” (of course you can also buy and manipulate it). Integrating a chat bot should be doable?
With a filter for bad words you could even read tweets from other players?
I can’t think of any game that would offer such a feature.
Crack users could get their own messages “Hey there, why do you not buy the game and support us?” day 60 error, this device will self destruct in 60 seconds 
Setup Wizard:
Some people like to lovingly set up every shop. Will become rather annoying and time-consuming over time, an agency for this (interior decorator) and ready-made templates would certainly not be a problem and rather a trifle?
Copy & paste own blueprints is already planned, will we able to share them?
Health Problems
I’m thinking of illnesses and their effects on the player character as well as employees and other people.
Imagine you have Corona, visit a competitor or their biggest store and cough up.
Injuries, e.g. from a car accident, would also be nice.
Little Adjustments
More salt content in the fries to sell more drinks, less filling food so more is bought, extra cheap imported clothes made by child workers, unpaid overtime, gemstones from african slave mines, furniture from illegally deforested rainforests etc.
A real capitalist is fine with any means and some people like black humor, even if it’s unfortunately realistic.
Sabotage, Emergencies and Disasters
Another big one. I’ve already written so much, but if you want a list I’ll be happy to provide it.
HQ: Accounting, Legal Department, Management, Secretary, Publicity Department
Same here as above.
I didn’t list family/dynasty, security stuff etc., that was probably suggested often enough.
I think that’s enough for now, it’s only about 2 years of work, if not more. I understand something about game development myself, but as mentioned at the beginning, almost every trace of “RPG” is missing, by which I mean more than energy, hunger and motivation. I guess some of the needed systems could be bought on the market, performance is another thing to think about.
It doesn’t matter how many business types or shallow possibilities there are, what matters is the soul of a game. Do you know The Guild 1? Some people have long-term fun by repeating the same monotonous activities over and over again, the majority probably prefer variety, emergencies, surprises. Imagine you have outplayed the competitiors and suddenly a “Ronald Dumb” appears and is more powerful than you…!
From a certain point (where everything is fully automated) you can stay at home right now, and not everyone likes crazy achievements. It doesn’t have to be a life simulation and you can’t please everyone, so as a final recommendation:
Make as much optional as possible. The two main factions of tycoons and Sims lovers can somehow coexist.
And last but not least: Modders can also do a lot of the content, if you build a corresponding API for factions etc., don’t wait till the end of EA. A friend of mine (“Souldrinker”) built a Mod-API for The Forest years ago that can be used for any Unity game, it’s open source as far as i remember.
I guess some good modders could be found somewhere, you could do a little competition and include them in the credits?
Sorry for the long text and any errors, mostly translated with google.
Dear devs, how big are your ambitions?
Greetings from an old think tank.