I question for those who would like the game to be a challenge - what is it that you would like to see?
Do you want balance change so that there is lower income through tax, higher building costs, more maintainance costs, increased traffic etc?
Do you want scenarios (Achieve 95% well educated within 5 years etc)?
Do you want win-states (population = 1,000,000, so you win)?
Do you want tougher maps (less buildable area etc)?
Do you want external interventions (aliens invading and blowing up half the city every 5 years?)
Do you want to see more constrained progression (effectively a tech tree locking off items until much later in the game?)
I'm curious, as I see CS:L as a sandbox rather than a challenge... meaning I enjoy it as the concepts of easy/hard are irrelevant for a sandbox... but while I've seen numerous threads along the lines of "the game is to easy", I think the more constructive threads would be "I'd prefer the play a game rather than a sandbox and I'd like and option to turn it into a game by doing X"
Yes I want to reach 1,000,000 cim population. Why? Because CO said it was the max and damit I want to reach the max, always! Now of course I can't do that because I run out of the ability to place the roads I need to reach that million cim target,,,,,,,,,,,,, but I digress.
Secondly I want tourism to work. On some level. Any level?
Now for the hard core. I want it to be more real world like. For example. I want to be building my city and then through referendums and votes by the populous I as mayor want to be encouraged to...............
Go clean energy
Repair/replace all bridges & roads due to their age
Have existing buildings become ADA compliant
Have existing buildings have to be retro fitted with sprinklers
Build bike lanes
Build bus lanes
Use drones
Build Trams
Build more parks
Maintain more green space
Provide free concerts in the park
Build parking garages/provide more parking
ETC, ETC ETC
In other words all of the real life things that city citizens vote on, want, complain about, get enacted, etc. I want that to happen in my city. Not directed by me. Just randomly by the cims. You know all those things you read or hear about on TV that other cities around the world are doing.
Now as mayor I know my cims want this, that and the other now it is up to me to fund those things they want to keep them happy. Or not. Again that would be up to me as mayor.
Thirdly: I would like there to be almost like an outside/larger government/world where by there are depressions & recessions, global happiness & sadness, cities that need bail outs or food or oil or ore or wood. Maybe I would have to (if I wanted to) provide an outside (pretend) city or country with trains or buses or build them schools or provide them with clean water. Or maybe another pretend city had an earthquake and they needed many supplies and my city could help by building more airports, providing more food, supplies etc. I don't have to see the city/country I'm helping. I'm just doing it to be a good citizen of the world. By doing so that would put a strain/drain on my own resources. So maybe I need more farm land or oil and maybe I don't receive the profits from those industries because I'm helping another land?
Fourth: maybe new industries could be introduced/enacted. Such as automobile factories or plane factories. Where I as mayor would have to provide numerous bonds to get those businesses up and running. Maybe I would want to help a company build a harbor or widget factory? Maybe in the building process there were bad managers of the project who stole all the funding and then I had to help keep the project going (or not) by passing more bonds or giving more loans? Maybe there could be a space program that my cims would want me to fund to send satellites into space to provide better cell phone coverage? Or for tourism trips?
To sum up:
For me I would like to see my cims (or outside influences) ask, demand, need, request many different types of things that my city could provide all be it at a cost. So maybe while I'm funding the new auto factory there could be a world crisis and a massive amount of food is needed and I would need 12 more trains to get the food there then just a few months later my cims vote to have bike lanes placed on all my city roads @ $X amount per mile then a little while later another city is in desperate need for clean water. I don't want to see it coming. I just want to try to manage all of the crisis-es as they happen. So to speak. If that made any sense.