You probably need to detach Britain, since we were too far gone already in terms of industrial development: if the landed classes had staged a last stand, they'd surely have lost.
So: William IV dies in Flanders in 1813, Ernest Augustus is horrible, confrontation over Catholic Emancipation or something, stones thrown at the army, one thing leads to another, Commonwealth of Great Britain and Ireland declared, 1832.
Meanwhile, somehow replace the pig-headed Charles X in France with somebody of Bismarckian sublety and Metternichian pragmatism, so that as of the British revolution there's been no French one. If we could suppress or avoid revolutions in Belgium and Greece as well it would set the best precedent.
So, House of Hanover flee to, ah, Hanover. The appearence of a revolutionary power which, in spite of its initial bourgeois respectability, is both significant and impossible to crush focuses the minds of reactionaries. With nobody inclined to mind what Britain thinks, can Austria, France, and Russia bash out a mutually agreeable brutalisation of the Ottomans? Austro-French concensus that Italy is a geographical expression, at any rate (which returned for a while after 1861, interestingly enough).
So, there's a way to keep the Holly Alliance somewhat functional for a bit longer than IOTL: it's a start. Proper union, now...
The union of the France-Germany-Italy-Benelux-Hapsburgia area in an economic and political bloc was being projected - by the Germans, the Germans, and the Germans, but still - from the latter part of the 19th century so it's not entirely outlandish. In the long-term it would probably help to dislodge Russia at about the time Britain's industrial lead is slacking, but for now, perhaps another common threat can be furnished by the United States? Some sort of disastrous endeavour lying between the final Spanish expeditions and Louis Napoleon's Mexican adventure?
And then the arrival, and defeat, of the revolution, and a further drawing together in solidarity. Some chain of affairs in Germany prevents Prussia having any second thoughts about the Austro-French hegemony. I don't even know what happens to Russia.
Now, the society of divinely-sanctioned hierarchy and the Vile Multitude not having any opinions cannot last long in an industrial world, but could a whole team of *Bismarcks and *Bachs and *Alexander III's arise, determined to modernise without giving an inch to the modernisers?
Meanwhile all the various *Marxes, *Kossuths, and *Garibaldis are gathered in the fog of London, and find themselves with a lot of government money at their disposal.