Actually if Germany and Austria alienate the way you propose than we ger 7 years war 2.0.
In this case I dont think Germany can afford to build a fleet: everything goes to the army and land defences if they want to survive. Allies are likely Brittain and Italy, maybe Ottomans and Japan.
A very desperate german warplan will depend greatly upon time even if we add another German army as TTL they didnt have the luxury to limit themselfs because of the only noble officers nonsense:
defend against France, try to slow down the Russian advance and try to knock out Austria as fast as possible - maybe supporting any seccessionist movement you can.
You can try the first with 3 armies and maybe the BEF, and Italy might help a bit as well at least as a diversion, 2 armies against Russia with better defenses in the area. The rest with Italy will try to finish Austria - occupation of Vienna and offering independence to Hungary and maybe Bohemia. They will also try to build on the german nationalism in Austria. Or if the Habsburg are willing a practically white peace as soon as possible.
As Austrian performance OTL was horrible and their mobilization pretty slow - according to their plan as well this might work and surely would be the only chance that Germany has. After beating Austria the forces there will be transferred against Russia.