Simple enough challenge, how do we get the Habsburgs to exercise prolonged rule not just of most of the length of the Danube and its watersheds, but *all* of them.
Incluiding the watersheds?
Hmm, so, that would mean, going at least by this map; in addition to its OTL lands it would also need to incorporate:
-Bavaria
-Entirety of Serbia
-Entirety of Romania
-Upper half of Bulgaria
Don't think it could really be that simple enough. Well, perhaps not with Bavaria maybe, but the others...
Or can it be Habsburgs not under Austria itself? If it's possible.
How about staying North of the Danube itself. The Danube serving as a border between herself and the Ottomans like say the Rio Grande between the US and Mexico. They could demolish the fort at Belgrade as opposed to keeping it. And focus on gains in the danubian principalities during the Austro-Turkish war before the War of the Quadruple Alliance.
The most obvious solution would be to make the Great Turkish War go even worse for the Ottomans, although I'm not sure how. Somehow kill off enough members of the House of Osman to cause a paralysing succession crisis and allow the Holy League forces to go around conquering territory with relative impunity?
Not likelyNapoleon III supports Austria against Prussia meaning they get South Germany and eventually conquer Romania and Yugoslavia after reforming under Maximilian I or Franz Ferdinand into the United States of Greater Austria.
The most obvious solution would be to make the Great Turkish War go even worse for the Ottomans, although I'm not sure how. Somehow kill off enough members of the House of Osman to cause a paralysing succession crisis and allow the Holy League forces to go around conquering territory with relative impunity?