He returned to fight in the campaign of the summer of 1813; Napoleon gave him the command of the Army of the South, assigned to contain the Schwarzenberg coalition. After the defeat at Leipzig (October 16-19, 1813), he returned to his kingdom. In January 1814, he signed a treaty with Austria.
At the Congress of Vienna of 1815, the generous monies he paid the diplomats, particularly Talleyrand, served no purpose. There was the possibility that the Bourbons might return to the Neapolitan throne. A desperate Murat looked for opportunities on all sides; he wrote a cordial letter to Louis XVIII and joined Napoleon in exile on Elba. The latter informed him of his plans to return. Murat declared war on Austria as soon as he learned the Emperor had landed. He soon occupied Rome, Ancona and Bologna. He launched a proclamation from Rimini, calling for the unification of Italy. Austrian troops, led by Neipperg, soon encircled him and he was defeated at Tolentino, on April 21, 1815.
Murat had to flee while Ferdinand regained the throne. He arrived in France, but Napoleon refused to see him. In Corsica, he assembled 600 men, enough for him to dream of reconquering Italy. He sailed for the Italian coast, landed at Pizzo and was taken prisoner. A decree from the king ordered the commission who tried him to allow him "half an hour to receive the last rites." Murat himself gave the order to fire, on October 13, 1815.
http://www.napoleonseries.org/articles/biographies/marshals/murat.cfm
These are the last years of the life of Joachim Murat. In January 1814, he had signed a treaty with Austria. Let's assume that he refrains from picking up again arms during the 100 days, and that at the Congress of Vienna he is confirmed on the throne of Naples.
Sicily remains under the Bourbons (at least for the time being). You have already a first major split.
The second one should be in 1849 (the 1821 insurrections never had a chance). The 1848 insurrectionary motes are slightly more successful, even if at the end they are crushed. However, Austria does not do so well in the war with Piedmont, which ends up in a substantial draw. One of the provisions of the peace is independence and neutrality for Milan (something similar to Belgium, with french, piedmontese and Austrian guarantee. Might be nice to have a republic: after the insurrection of March 1848, the moderates were successful in gaining power and asking for union with Piedmont. In TTL, the moderates loose the power fight, and the revolutionaries never ask for the union). The second provision, however, is that Piedmont too looses something: Genoa regains independence (again as a neutral, guaranteed republic).
Mazzini gets to be practical for a moment (almost ASB

), and instead of proclaiming the Roman Republic (which is doomed from the beginning) proclaims a republic in the papal lands of Emilia and Romagna. Given the slightly different political sentiment of TTL, this republic is accepted.
Mind, it is very unlikely that all of these small states might last in the nationalistic climate of the mid-19th century. It would be interesting, though.
If you are willing to stretch things even more, by 1900 both Milan and Genoa are "associated" to Switzerland (not as cantons - it would change too much the ethnic and religious status quo), under a guarantee of perpetual neutrality.