So here's a list on the military numbers expanded out from the forces which will be initially in play-
Germany Wave 1: 6,000,000
Germany Wave 2: 4,000,000
Italy Wave 1: 1,800,000
Italy Wave 2: 3,000,000
Spain Wave 1: 600,000
Spain Wave 2: 600,000
Allied Forces Wave 1: 8,400,000
Allied Forces Wave 2: 7,600,000
Allied Forces Total (theoretical): 16,000,000
Russia Wave 1: 5,800,000 effective(out of 7,200,000)
Russia Wave 2: 4,800,000
Austria Wave 1: 1,900,000 effective (out of 2,400,000)
Austria Wave 2: 2,400,000
Austria Wave 3: 2,400,000
Scandinavia Wave 1: 500,000 effective (out of 600,000)
Scandinavia Wave 2; 1,200,000
League Forces Wave 1: 8,200,000 effective (out of 10,200,000)
League Forces Wave 2: 8,400,000
League Forces Wave 3: 2,400,000
League Forces Total (theoretical): 21,000,000
This is a bit less of a rosy picture numbers wise, but we'll have a qualitative advantage and a notable edge on mobilization speed. We can absolutely win this war, but only with an aggressive strategy which emphasizes our strengths. Aiming to knock out Austria will be crucial, or at least taking Vienna and leaving their Alpine forces unable to hold against Italy and Spain, which opens up about 6,000,000 soldiers for use somewhere other than Alpine passes.
We can and should be on the offensive wherever possible though, to take advantage of our early edge and to encourage revolts and anti-Imperial action in enemy territory, especially Poland, Bohemia, and Austria proper.