In the case of the Brusilov offensive, the Austro-Hungarians had transferred all their good units to the Italian front for their own offensive against the Italians.
What was meant as a Russian reconnaissance in force turned out to be a total rout of the remaining very low quality troops of the Austro-Hungarians, very much to the surprise of General Brusilow.
Any such thing staged at the Western front would result in a mass slaughter of the attackers, nothing else. Only when you can convince the OHL to send 80% of their soldiers on harvest holiday, there might be a chance of success.