Hmmh, I am really interested to see what led to the disaster in Saxony at which you keep hinting. Your setup there seem very solid. An army this huge, concentrated in one place is virtually unbeatable with what Prussia has at its disposal.
But perhaps size was exactly the problem here. What if winter closed the passes to Boehmia for an extended period of time. Dresden alone would be unable to feed such a big army. You would be forced to take desperate actions - most likely an attack against Leipzip in order to find more supplies. The Prussians might just beat the Austrian monster army in a defensive battle if it has been weakened by a march through the snow/starvation/some inactive corps commanders not participating in the attack.
After this initial defeat and with units starving, the Austrians would become easy prey. If the passes were still blocked, annihilation would become a distinct possibility ...