I've got an idea for a game that I'd like someone to make:
You play an infiltrator, a government spy aiming to work your way into an organised resistance force, gain their trust and work your way up their ranks while supplying information to your fence (that's not the right word for a spy handler, but what is?). The higher up you go, the more difficult it is to remain hidden as you have more eyes on you, you're leaking bigger secrets, and you're decisions inside the organisation have greater impact. You'll need to tow the line to a certain extent; at which point are your colleagues going to realise you're deliberately making a hash of their work? When are they going to realise that crushing defeats they face are due to facts only you could have let slip? How can you dispose of people who suspect you without raising more suspicion?
Perhaps it is an evil empire and a heroic rebellion, like in star wars; perhaps a peaceful democracy and a warmongering insurgency; perhaps not even so black and white. Perhaps you could have the choice of infiltrating the government or the rebellion; perhaps you could even have the choice of playing as a double agent and defrauding your fence. I think there would need to be a cut and run option, where you end the game and reveal how close you were to being caught. There would probably be a dwarf fortress style 'built to spill' mechanic, where it's really just a case of not if but when you are caught. Or gain control of the organisation, and set your mining in secret missions against each other and hope they don't talk to each other in the mean time. You'll have to build up enough trust in them, and under mine their trust in each other, to achieve that sort of victory.
I see the game as being fairly procedurally generated, with freeform and unpredictable gameplay emerging from particular choices you make and randomised NPCs. It could be anything from a text adventure to an open world sandbox city/country. There might be structured missions along the way, which might have their setup affected by the current works you inhabit.