Hello you wonderfull people 
First of all - I really like the idea behind this game. I think this game hase a huge potential!
Also i am aware that the game is still in developement and everything is suspect to change.
Second - I’ve read a lot of suggestions so far. Some of them had the same idea as my suggestion but with different approaches.
I’ve played now for some hours and after some time it feels like there is nothing really challenging. You have your constant income and there is no way to mess things up.
So here is my suggestion:
As in the real world, there should be some risks when running a business.
- Your business/warehouse could get robbed (already on the roadmap if i remember correctly)
- There could allways be a fire/water damage to your shops/warehouses
- Furniture or workstations could break and you would need to repair/replace them
- Angry customers could vandalize your shops
- Other negative events - feel free to comment on this topic
You could also add a way to reduce the damage to your wallet by adding insurance which you would pay on a (maybe) weekly bases. The insurance would not (!) cover the full 100% of damage.
Also there could be a risk that employees just quit their jobs (because they found a better paying emploer?). After, lets say, 3 days the would then leave your company.
To prevent things like this you could be able to pay your employees a bonus or give them some reasons to stay at your company. Maybe you could use them company cars or other things? Feel free to comment your suggestions as well!
Either way, what i want to say is: As far as I know, this game want to be a simulation (on steroids), so why not consider real world risks of running a busioness 
I know that all these things could be a whole patch in its own and i want to remind you that this topic is just for inspiration. (But it would be cool to have some mor challanges. Sleeping for a whole week and buying a supercar is not the gameplay i want)
Best regards