I just thought of something.
You know that Dirve your character has in Trail of Cthulhu? It's there to give the Keeper something to point to and prod you with to go head first into danger. Right? According to the rules you take a penalty to enforce your free will as a player, and not act in line with the character psychology you have on your sheet.
That sounds a lot like things I was pondering in my posts about free will. Sure, it does not involve NPCs or other PCs influencing your PC, but the Keeper. Interesting territory, indeed.
I don't think I have seen anyone comment upon them in that light. In my CoC games I have not yet remembered to use them! Interesting.