MittelEuropa was more about political control than economic benefit, it was to provide buffer states between Germany/AH and Russia that could also help avoid the worst aspects of a blockade in wartime.
There were inbuilt stresses, German agriculturalists wanted tariff protection from cheap AH agriculture and AH industrialists wanted tariff protection from efficient German industry, so that will have to play out one way or another.
Setting up independent states as wartime expedients unleashed nationalism in those areas. Germany setting up the Kingdom of Poland from late 1916 resulted in a state that defeated the Soviet Union a few years later. Similarly the Baltics, Finland, Ukraine and Belarus walked their own paths in the chaos of the end of the war in the east and the formation of the postwar order. This will be different in a CP victory, but momentum will have been created and will have to play out somehow.
The US enacted a Defence Act and a Naval Act in mid 1916, doubling the size of the Regular Army, quadrupling the size of the National Guard and authorising the almost simultaneous construction of 10 battleship, 6 battlecruisers and 10 light cruisers to be ready 1921-23. Even if the US doesn't join the war, indeed especially if it doesn't, by 1922 or so the US will be default become a world power and rub up against Germany who has also drastically increased its power to support the hard power tools it already possessed. I struggle to imagine a peaceful agreement like the Washington Treaty in this scenario, or at least one like OTLs.
Reparations payments might be a problem for the former Entente the way it was for Wiemar Germany. Will Imperial Germany march into France if they default on payments? What about if Britain defaults, will they march into a Dominion?
Of course all this is better than the Holomodor and Holocaust. Just sayin.