I produced exactly this kind of chart when engaged in a semi-hostile management take-over, including the wild guesstimates of probabilities.

But then I further did a stability analysis to see which of the probabilities needed to be more accurate, and thus require more careful measurement. That identified critical decisions and pathways, and which of the other party's decisions should be nudged.

Here, though, there's not really a lot to be gained by greater precision, although your point is taken.