I'm a bit surprised that MrP haven't pointed out any mistakes done be my, yet.
He is, after all, the resident Great War expert.
So, what does he think of this?
I'm here! Though I'm hardly an expert - merely an enthusiastic amateur. I recommend killing
Henry Wilson in the Boer War or Third Burmese War before he can help France. He did more than anyone else in the UK to get Britain into the war. Without Wilson there are no mobilisation plans, no discussions with the French general staff - which he performed in detail, without instructions from his superiors and which clearly exceeded his authority hugely. The British official position was always, "We do like the French, but we can't have any proper discussions or we'll be tied into a war we might not want." When news of Wilson's discussions were revealed to the Cabinet IOTL several members were quite angry. IIRC, only the PM, Foreign Secy and Secy of Defence had been aware beforehand. He was a huge Franchophile, and used to go for cycling holidays on the continent planning where every bit of the BEF would be.
So, yes, kill him for starters. Pre-war French expectations were that the Germans would launch a shallow attack through Luxembourg and possibly the bottom of Belgium. The French were themselves constrained as Wilson - and others - made it clear that for France to attack via Belgium would ruin British support for the war. So France opted for an attack on Alsace-Lorraine, which got mangled by the Crown Prince, who then insisted on being allowed to attack. This was contrary to the grand plan, but von Moltke was too weak to say no, so he left it in the fella's hands.
Keep Joffre out of the top spot and you can weaken the French army considerably. Beware Victor Michel, too, Joffre's predecessor, as he wanted to use the Napoleonic demi-brigade system - half regular units, half reserves - to increase the number of available divisions. IOTL
Gallieni refused post-Michel command because a) he was old and infirm, and b) he had been one of those trying to get Michel removed, so he felt it'd be dishonourable. I think he's probably a flexible mind, so have him appointed but then get ill, messing up any reorganisation he attempts.
A lot of the pre-war French stuff can be left the same. They had no attached medium and heavy artillery for divisions, just billions of 75mm guns - well, 36. Anyway, they also had an asinine doctrine set up shortly before WWI which meant artillery prepared a position for assault, but didn't support the infantry as they went in. Add in the crazy offensive a l'outrance of the French army of the period, and you're all set for them to beat their brains out on the German defences.
IOTL German plans called for their forces to retreat to pull the French forward, thus facilitating the grand envelopment through Belgium. With no envelopment being contemplated, I think Germany will adopt a less elastic defence in the West ITTL.
Right, Russia! I'm less up on the Russians. They were aware of their shortcomings as a result of the R-J War, and kept more artillery ammunition close to their guns instead of in depots than the Germans. However, the Germans probably have deeper reserves.
This place has a thorough and very cool breakdown of the Russian Army. I don't have a similar online breakdown for the Germans, but I can dig stuff up for you. Russo-French war plans called for both armies to attack in the first 15 days, IIRC, in the belief that the Germans couldn't possibly hold them both back. OTL proved them wrong.
A benefit ITTL for the Russians is that German forces are so overwhelming that the initial Russian attack will be flattened and pushed back into Poland almost at once. However, this will mean that they have to cancel their attack on A-H, and throw troops north asap. With the Italians bribed, the scenario looks rosy for the A-H chaps.
Look forward to more!