That's a good challenge, however is TWO Sicilies, not TWIN Sicilies.
Before embarking in such enterprise the kingdom should go under massive reforms, maybe a successful sicilian revolution of 1848?
Sadly this period of Italian history is only told in Piedmontian perspective.
This is probably the best way forward. You'll need someway for the revolutionaries to keep up the good fight; IOTL Ferdinand II crushed the revolution in his capital and later in Calabria and Sicily. A good POD might be for Ferdinand not to force Pepe to resign as PM of the newly formed liberal government under Ferdinand's new constitution. Ferdinand is still forced to bow to popular pressure to join the war against Austria, however with Pepe in charge of the government instead of leading the army he's better able to organize and supply the force, so that when the Neapolitians begin their march it's a 40,000-strong corps as promised, as opposed to the 14,000 he got IOTL. As well this force doesn't waste time sitting on the southern bank of the Po waiting orders from Naples, and instead continue their march towards Venice; the small flotilla (consisting of 14 ships as opposed to seven IOTL) that accompanies arrives in Venice on 16 May as in OTL, with the ground forces marching into the lagoon on 20 May, nearly a month ahead of IOTL. As in OTL immediately the Venetians join their forces to the Neapolitians, making the combined Italian army in the city nearly 60,000 strong - three times the size of OTL, with the majority of the troops being Neapolitan, and only a sixth Venetian natives (the rest are volunteers from the other Italian states).
However Sicily still declares its independence from the Bourbons, as in IOTL. The Sicilians reject Ferdinand's constitution, which is heavily based on the French Charter of 1814, and instead demand a return to their own constitution of 1812, and full political autonomy from Naples, with only a dynastic union joining the two.
Back in Naples itself Ferdinand still tries to crush the revolution, calling up some 12,000 troops into the city center, while radicals throw up barricades throughout the surrounding districts. However the loyalty of many of these units are in question, and when the King gives the order on 15 May to attack he finds many of his soldiers turning to the other side. While his Swiss Guards, and the
lazzaroni, the Neapolitan permanent poor classes who are dependent on the good-will of the monarchy for their sustenance, are loyal, even fanatical, his regular army troops are not so much, and when Pepe and some hundred other deputies organizes a resistance at the Monteoliveto district's municipal hall, the battle is all-but over. By three PM the loyalists are forced to fall back, and Ferdinand has to retreat from Naples to Capua, on the other side of the Volturno.
With Sicily breaking lost, Calabria in flames, and Naples itself lost, Ferdinand is forced to resign, passing the crown to his twelve-year old son Francsis II under a regency of Ferdinand's younger brothers, Louis & Leopold.
After that, butterflies, butterflies, the Sicilians are brought to heel in some fashion, the Austrians are ultimately defeated by the combined arms of Naples & Savoy, though the two erstwhile allies immediately have a falling out over spheres of influences in the new Italian order, relations with the Papal States, especially after the Neapolitans join the French & Spanish in putting down the Roman Republic, and, ultimately, leadership of the Risorgimento. Francis proves to be just as weak of a ruler as he was IOTL, however ITTL he's under the influence of his uncles, not his step-mother, and while Louis is brutal (he's not called
Il Bomba for nothing), between the two of them they're pragmatic enough to work with the new liberal order.