It's only after war breaks out that old grievances and rivalries flare up, fuelled by a universal feeling that at least one neighbor had appeared to be preaching peace and then revealed themselves to be a warmonger - the French felt that way to the Germans, and the Germans felt that way to the Russians
This. There is actually a decrease in European tensions over time and noone expected the Sarajevo incident to get out of control.
A few other issues.
All metal aircraft will not be a thing, at least at any scale. The metal production levels just are not there to make things common. Its not common through most of the interwar period and very few places have the Al production to make it viable at scale.
Warship propulsion is shifting over to oil for them as have access to it so any numbers count has to include the issue that a coal fired ship needs around 60% of the crew as stokers and an oil fired one about half that ( freeing up crew for gunnery, radio work, range finding etc.) And the oil fired ship can go further faster with less issues on refuelling.
The French will be expanding their artillery to include lighter howitzers. There is a fairly complex dynamic going on here but the major issue is the germans expected to meet fairly substantial fortifications, hastily built, 1m of overhead concrete being the metric - static target you could engage with light howitzers the French did not so the procurement emphasis was different. Until you get a very quick fire control system for the artillery you need a static target to engage with howitzer fire. As things move from shouting and waving flags for control to laying phone lines quickly this happens. They will also be looking at AFV and mechanical transport far faster than the germans as will the British ( who had already decided to move to MT as much as possible after the Boer war.)
Incidentally horse drawn kit is actually more tactically mobile than motor vehicles in many circumstances, less so in NW europe.
All of this is capital intensive and the German and Austrian issue will be getting the money. The Reichstag had already balked at funding the 1913 bill and actually had no way of paying for it. Everyone has the issue but the bigger the army the bigger the issue. Britain and France have the most developed financial systems ( generally and in terms of parliamentary debate) and biggest automotive sectors.
They are also more likely to learn more quickly about aircraft capabilities and useage. For the colonial powers having aircraft is probably a cost saving very quickly and for the British they had already decided on a big investment in naval aviation - incidentally incendiary ammunition vs airships was regarded as quite acceptable. The High Seas Fleet is the target, Taranto and Pearl Harbour did not come from nowhere. The dynamics of hunt the raider change with the first aircraft carrying ships and with no treaties easy to see lots of experimentation with numbers and sizes.
Semi auto rifles probably not. Everyone had been looking at them noone was really keen. To reequip a millions strong army is a big undertaking so there has to be a clear advantage to the average conscript. Especially with everything else going on and with aircraft demanding lighter weight MG issuing one of those to the infantry platoon instead of 30 semi auto rifles is a good start, which is how the Lewis gets its start.