And they likely are not even this simple - but with this structure there are questions raised about what we need to know in order to understand the causal structure enough to know when the Cause will result in the Effect, such as whether the other variables in the path are possible (X1, X2, Y for example).
With this causal structure the variability in the effect being measured for the use of CPM (Cause) is impacted by X1 and X2 and Y,and a minimum their existence, perhaps even their nature or own causal structure. In which case we do not want to close the door on Cause -> Effect until we understand that structure and have studied the system effectively.
Ok, that is enough laps around the track for this morning. I realize I have come full circle -and still have not decided, after months of pontificating, whether anything on this list can be removed due to justifiable evidence of the negative.