Interesting thread, starwed. I'll have to look at it more closely.
One idea that occured to me relates to criticals and fumbles - I'll call it "Double Down." The idea is that you take a chance on turning your fumble into a success, with a second failure leading to a potentially disastrous result. It's kind of like a crit confirmation - you make another opposed skill check and if you win, you get an opportunity to reverse the situation into a better-than-average success, but if you lose, the chase is probably over, and you are in a threatening/dangerous position.
For example - let's say you're chasing someone through the streets of the city. You roll a 1, or your opponent rolls a 20, and the DM says "OK, a shop door opens unexpectedly right in your way, and you run into it full tilt! You lose more ground picking yourself up off the ground."
You: "Hang on, I'll double down."
If he wins the next check, maybe the bad guy looks over his shoulder and runs smack into a bystander, and has to pick himself up off the ground, too.
If he loses, perhaps he dodges out of the way of the door and into the street, but unfortunately, he takes damage from getting runover by a cart, and his pants leg gets caught in the axle, and he's being drug in the opposite direction.
