So, a long time ago, I began with the idea of a Conflict Web.
Make up any two characters, write down their names, draw a line between them, and why they’re at odds. Next, draw a line out from either one of them, and add another conflict. Feel free to keep adding lines and expanding until you have a clusterfuck of problems. Bingo, you’ve got a situation you can play with without having to write out all the possible outcomes- just play the characters according to their motivations and tie in the PCs as part of it, and play flows naturally.
I used that basic concept to build the Well of Souls scenario for HeroQuest, though I wasn’t very clear about another idea that goes hand in hand with it. You probably aren’t going to use all of those conflicts, most likely, the players are going to focus in on just a handful as fun. That’s ok, having that variety is what gives them choices.
Now, here’s a step further. Make a conflict web for 3-8 characters, all political leaders in a city, nation, or whatever scale fits your game. Now make a separate conflict web, for the folks just a tier lower than them in the social scale (again, 3-8)- maybe they’re lieutenants, followers, etc. Finally, make a conflict web for the folks just below that.
Now you have a crunchy situation that is good for a full campaign. Give the players a general outline of what the situation is, and ask them what tier they’d like to play at.
Or, maybe they can play with three characters, one at each tier.
No matter what, you have a web of conflict and intrigue waiting to happen.