Okay, a new idea for Marionettes:

Marionettes is a game about morality, as the Puppets and Puppeteers embody them. The Puppets are governed by Principles, which are static rules by which they act. The Puppeteers are governed by Desires, which they impose on the Puppets. Desires aren't necessarily bad, nor are Principles necessarily good, but it's easy sometimes to paint them like that.

Characters: Maybe each players gets one Puppeteer and one Puppet; then the Puppets act in their world, for whatever reason, while the Puppeteers manipulate them from above.
The game's gimmick is that the relation between Puppeteers and Puppets isn't one-to-one; a Puppeteer can maneuver whatever Puppets he wants in order to promote his Desires. The Puppet, of course, is free to resist the Desire based on his Principles.

In a perfect world, each Puppeteer and Puppet would be clearly differentiated from the others by a 'signature' Desire or Principle; maybe Setang the shadow puppet's Signature is the Principle "Always act to promote truth over falsehood", and Billy the Puppeteer's Signature Desire is to "Amass wealth".
Then, maybe Setang and Billy would come into conflict when Setang is trying to buy something from someone; Setang knows he can easily pay the asking price, but Billy's Desire wants him to try to cheat the seller by bargaining, finding nonexistent flaws, pretending poverty and playing on his pity, etc.
There'll probably be some non-random system - resource allocation, maybe, or bidding like in Zak's Courts and Corsets, coupled with some kind of comparison of the static intensity of Principles/Desires, for resolution. This is likely to be one of my ideally-GMless games, as well.

Now, I want some relationship between Desires and Principles above the individual level; I'm trying to think of how they would propagate. Maybe Desires float around like water; when they are satisfied, they decrease, but another Desire increases, while Principles reinforce themselves somehow, but are damaged dramatically when they contradict each other. Some process should also allow Desires and Principles to change in nature as well as intensity.

Maybe this can tie into the reward mechanic; perhaps there could even be an ultimate goal of Puppet/Puppeteer harmony, where Principle and Desire never contradict, and a reward system to that end.