As far as I can tell, the best way of accomplishing the PoD would be for Germany to have a strategy far less reliant on a quick victory in France before Russia can mobilize: in other words, you need to butterfly the Plan Schliffen away and have Germany adopt a Russia First strategy. This way, when A-H declares war to Serbia, Germany does not feel obliged to rush and declare war on its own initative to Russia and France both when Russia mobilizes. They let Russia declare war on A-H, then they declare war on Russia, and let France declare war on Germany. Neutral Belgium is never violated (or if it happens, it is France to invade when they get a bloody nose in Alsace-Lorraine), Britain stays neutral, and A-H can claim it is defending itself from rogue nation thaty harbors terrorists, while Germany can claim it is defending an ally. With Belgium left alone, and Russia the first great power to declare war to another one, the CP position looks much better to neutrals. As an additional benefit, with Britain neutral, and Russia and France declaring war first, Italy shall be bound (and willing) to be true to the Triple Alliance.