The problem is the same as with any no-WWI-thread: Whatever averts WWI during the July crisis doesn't avert a different WWI on the next crisis.
The true reason for WWI is the strategic situation: France and Russia threatened to attack Germany on two fronts. The German defensive strategy was based on the following assumptions
1- (likely correct) Russia would be the more difficult to beat the longer they waited,
2 - (likely false) - an offensive Strategy was pivotal to victory
3 - (likely correct) a quick victory over France required marching through Belgium
4 - (terribly false) The diplomatic fallout of the violation of Belgium's neutrality could be contained
5 - (false, but had no direct consequences) Russia's mobilization take so lang that they could beat France before the war on the eastern Front began.
So to prevent WWI, you don't just have to change the course of events during the July crisis, you need to change the German defense concept.
IMO one very plausible option is turning away from Austria - removing all collisions of interest with Russia and Italy and keeping the option of annexing the German speaking parts of the Austrian Empire after its dissolution.
Edit: The quick mobilization of Russia did not directly affect the western Front, since the Germans won Tannenberg and AFAIK did so without the units that were transfered from the western front. So the false Russia-can-wait-assumption did influence - albeit not cause - the failure of the Schliefen Plan.