So I've recently read that the Germans had the opportunity to encircle not one but two French armies in late August and beat up on a third. The armies in question are the 3rd Army in Verdun with the possibilty of forcing the 6th army out of its fortifications on the Moselle and into an open battle nearby while the Germans also missed an opportunity to encircle the 5th Army facing the German right wing. Is it ASB for the Germans to pull off this combination of blows? If not what would be the impact of such a series of defeats? I read that had the 5th Army been encircle this would have led to the right wing hitting Paris from the north instead of moving to the east.
There are several issues with pulling this off. First of all, the German 6th army was attacking straight into the teeth of the French fortifications along the Moselle, which had the same results as the earlier French attacks into Alsace. It was impossible to frontally force their way through those forts.
The French 3rd army was the most vulnerable, provided a different set of attacks are used, which I explored in this time line:
https://www.alternatehistory.com/discussion/showthread.php?t=128340&highlight=lorraine+offensive
As it was, the French just ran quicker than the Germans could follow. There is no way to make them stand fast in this era before full motorization and the French had intact interior lines of rail, which the Germans did not, thanks to the Belgian sabotaging their lines as the Germans advanced. Ultimately it would take the French being extremely stupid to pull off even one or two of these and fully ASB for all to work. Ultimately the Germans did make their mistakes too, which resulted in OTL, but the French messed up just about as much as humanly possible, but still could not lose despite it all.
Paris is another problem in Schlieffen plan scenarios. It was heavily fortified and garrisoned, which meant that the Germans would need about 250,000 men to besiege it (their estimates), which means that any scenario would require the German army to have an additional two armies in the West for this even to be possible, something which could not have been supported logistically.