One game idea I had from a long time was about controlling a "for-hire" special police force. Essentially, your guys are professionals in law enforcement and military action paid by governments to clean up cities and towns which are pretty much taken over by the criminal element.
The gameplay would be like X-COM Apocalypse, with a Cityscape you must deal with. Its pretty much X-COM Apocalypse without the aliens and only turn-based combat.
I'm split between having a single enormous city or a campaign where you must start on smaller cities and meanwhile accumulate money, tech and manpower, until you finish on some large megalopolis. Possibly with some factions carrying over the campaign.
Every city has factions. Government factions like Government, Police (sometimes multiple kinds of), The Military, Secret Agencies (think FBI and CIA), Political Parties, etc. You have to cooperate with the government in order to receive funding, but every faction in government has its own goal and not all of them are exactly on your side, or convinced of what you are doing.
You have Standard Operating Procedures, which are rules you must comply with it in order to continue operating. If you fail, you lose points. Things like not causing mass destruction, killing civvies, attacking govt forces, etc. One idea is that your SoP starts very strict and you can use your goodwill with the government to gain more policing powers.
There are also Economic factions. Say, Corporations which produce and sell goods, Cooperatives, Transport, Utilities companies, etc. However, some of them are actually being used as criminal shells.
There would also be other groups, like the Press, NGOs, etc.
Then there are the criminals. Gangs, lots of. From simple gangs of thugs to international mobster. They can also fight one another and do so, frequently, but they can team-up as well.
The forces of crime have an edge: They can infiltrate the other factions. Every faction that a gang infiltrates, makes the gang stronger. For example, if a gang infiltrates the Military, it will get military-grade weaponry and the corrupt military officers might even launch attacks against you.
Secret Agencies have their own enigmatic agenda. In theory, they are on the forces of law. In practice, their own private agendas often make them help the criminals and screw the lawful factions. They can also infiltrate other factions, just like the criminals. You can't attack them like the criminals, you have to play the game in smarter ways - say, finding proof of links between the criminals and the spooks, getting your govt buddies to make the spooksters back off, offing the right people, getting them to attack another faction, etc. You have to either curtail them or make them get cut off from official sanction.
The setting is near-future post-cyberpunk. Think 2050-2070 or so. Technologies better than modern world, but nothing ultra-outlandish. Maybe some cybernetics and genetic engineering.
You would also be able to "go rogue" and tell the SoP to fuck off. This turns your group into Rogue Police, so pretty much criminals. This is pretty much extra-hard mode. If you keep at it, the government will straight out order the military to roll tanks and kill you.
I'm thinking there would be "Multiple Endgame Scenarios", which culminate in a last epic tactical mission against Criminals or the Government forces.