Yeah Serbia is ratshit, but I can't help but think that if Germany defeated France in a single season the French would ask 'what if we had that heavy artillery we'd started buying in 1914, and or those 2 extra corps from Algeria?' and delude themselves that they were a whisker away from not losing in a single season (which they likely were). Similarly Russia would wonder if they implemented plan 20 and a few extra railway tracks if they'd hang on for the long fight.That's more-or-less what happened to France for about 20 years following the Franco-Prussian war and I don't imagine the German terms are going to be any more generous in this scenario. Whatever their performance in the field, the Serbs are going to be thrown under the bus at the peace table. Without French empowerment, the Russians will be grounded and unable to go clubbing in the Balkans.
Britain will likely remain at least semi-independent, on the grounds that they only needed to Copenhagen the KM and send more divisions with the BEF.Is Britain going to choose to continue to hang out with that bunch of losers, or hang out with the cool kids with their shiny uniforms and epic facial hair?