I was just flicking through the NPC rules to create my Limbo alter-ego, Bob the Scrooge, when I had an interesting thought. Playing Kingmaker but starting out with NPC classes instead of the regular classes.
The group would perhaps be local celebrities in Brevoy, or are otherwise plucked from obscurity to embark upon a stirring quest!
One important note; I'm not offering to DM this, as I don't have the AP! However, I thought it might be a cool idea.
I've been doing this to some degree in my game, at least with their tertiary characters. Wolves (and other wandering monsters) chew through them like popcorn.
Not saying that's a bad way to go, just be forewarned that their ability to cope with a crisis is not what most are used to.
That's something I've been wanting to do for some time as well, but with a more mundane premise than Kingmaker. Rise of the Runelords and Age of Worms are perfect in my mind, featuring characters starting out as residents of small towns and being drawn into the bigger world around them.
I wouldn't have put Kingmaker in that category, since the PCs will be marching off to adventure on page 0, but the idea of a king coming from such humble beginnings is kind of appealing now that you mention it.
My twist would involve changing the location of the Stolen Lands...
...to a Darklands vault. PCs would be plucked from the dregs of drow society - misfits, prisoners awaiting death sentences and given a chance to make their own way. Either they carve out their own demesne for the glory of their House, or to destroy those they once called ally.
