Servus and Greetings fellow city-building friends!
It is just a pitty that there is only one discussion topic (way to empty for such a nice game) so I decided to open up a secound. :)
I´m not sure if my suggestion is befitting for the game vision, but I thought that some kind of politcs system would greatly increase the options and customisations in the game.
A short example:
You, as wise ruler of your little kingdom, can decide the form of goverment (monarchy, republic etc.). Which goverment you choose has various impacts on different matters.
First: your titel (eg. in a Monarchy (in dependance to the size of the town): baron, count, duke, king, emperor).
Secound: different extra building options; a republican leader might build an city council hall (happiness bonus), a parliament building (choose between various republican laws with different boni) or a statue of freedom; a monarch might build the Imperial Palace (choose between monarchicel laws ), the Royal Gardens (happiness bonus) or the Empires Armory (bonus to heavy troops)
Third; different special uinits; e.g.: monarchy (Imperial Guard, The Empeors Choosen), democracy (Presidents Honor Guard, National Guard)
Forth: quests and tasks from your advisors (monarchy: state council), republic (parliament); eg.: Your state council is worried about the rising crime in the country, build an guard post! If completed upon the DATE you receive X happiness + productivity bonus fro X days; if you fail to complete the quest there will be an happiness penalty
Fifth: different UI overlay; monarchy: darker tones with red, purple, gold; republic: more lighthearted with blue an white
This are just some examples you could make use of this system and I assume there are many more. Neitherway I do fully understand if this concept does not fit with your game vision at all, I just took an inspiration from your front page (the citizens are awaiting ther wise ruler; enter the realm your majesty). If this dual goverment system is to complicated to impliment you may just take parts of it (eg. the quest system or the various titles referring to the city size).
Have a nice day and stay healthy!