I think a much better approach is to assign models to the problem ...and then have a probability distribution over models...It's true that probabilities-of-probabilities are just an abstraction of this

Isn't Chapman's approach and your approach completely identical?

As per OP's graphs, each point on the X axis represents a model and the height of the blue line as the probability assigned to that model.

Or did you just mean that your way is a better way to phrase it for not confusing everyone?