... and wait for the French and Russians to declare war on him - which they probably won't. So it never spreads beyond the Balkans.
Au contraire, I am convinced that once Austria-Hungary invaded Serbia (they actually didn't wait for their own DOW on Serbia) the whole machinery of alliances goes to work as it did OTL.
Russia won't let AH punish Serbia and diminuish their main ally on the Balkans (though it is an interesting question how long a pure AH vs Serbia war would have taken!) - maybe if they had attacked mere days after Sarajevo, but not the way they did.
Germany wouldn't let Russia destroy Austria-Hungary. They perceived them as their only reliable ally and feared a conspiracy against Germany.
Now, Eurofed would love them to throw up the cards of alliances that way (becoming Großdeutschland and safe the alliance with Italy), but that would have been seen as completely ruthless. Especially after signalling AH the full weight of German support (one point at which they war could have been avoided).
And with Germany and Austria-Hungary at war with Russia, it would be now or never for France.
@Blairwitch:
You are completely right. They would be seen as geniusses now if they acted that way.
A re-direct of mobilization would have been difficult, but doable. I imagine it the way that most of the trains go on schedule towards the West while those troops which can be easily re-diverted move eastwards.
As many troops as possible march southwards (through difficult terrain in the Eifel and Hunsrück) towards Metz, bolstering the defense against France.
The rest marches northwards into the Rhineland and take up camps in the triangle between Aachen, Cologne and Düsseldorf. Supply gets re-directed there instead into Belgium.
As soon as the initial mobilization is over or cut short, division after division gets picked up on the Rhine and sent to Silesia and East Prussia. We are now probably still in August. Directly after the battle of Tannenberg, we would have a situation where, when compared to OTL, the German commanders in the East would be swamped with disposable troops. Now they did well with what they had OTL, the possibilities are huge if they don't make grave mistakes.
The French plan XVII would have no reason to be any less of a disaster than it was. There might be limited counterattacks to improve the frontlines (especially considering the terrain).
If we assume the best case scenario of British neutrality, then there is no blockade. The CP could decisively improve the management of its economy, avoid most of their hunger-crises if not all of it and keep a higher morale on the home front.
The loss of colonies would be restricted to those in the French vicinity, Togo and Kamerun, maybe the possession in the Pazific.
German counteroffensives in the east could start earlier, thus still in autumn instead of winter. This would at least ease the Austrian desaster in Galicia. In a best case scenario, we would see encirclement battles in Poland and the capture of not only Lodz but maybe also Warsaw - all of that in 1914.
Under such circumstances, Italy and Romania might remain neutral. 1915 might see CP advances into the Balticum and the Ukraine which would make the Tsar sue for peace (unless Britain sooner or later still enters the war).
By autumn 1915, France might be alone... in well-defendable positions, but in no hope of winning.