Yugoslavia? Definitely a bridge too far.
I suppose so, but Soviet aid on the level of the OTL Spanish Civil War (supplying aircraft, tanks, artillery, munitions, arms, etcetera) would not be too unfeasible and if there were large defections from the Royal Italian Army then the Communists would perhaps possess the expertise to operate more complex devices effectively? If not, a more interventionist Soviet Union could send their own version of the Condor Legion and volunteer units to fight without officially partaking in the war.
The problem with a communist Italy was that unlike fascism there is no a single clear leader who can organize the movement, just see how they react during the Matteotti affair, totally without leadership or any clue.
That is a very intriguing point. During the Matteotti affair, a general strike was threatened but Victor Emmanuel III stayed firm as Mussolini was supported by a majority of the Chamber of Deputies and the Senate he stayed firm; a dismissal could have led to civil war between the Blackshirts and the rest of the Italian government.
Let's say with a POD sometime in 1923 or early 1924, Matteotti is still killed in late 1924 (or butterflied to sometime in 1925), but the Socialist and Communist movements are somewhat more cohesive and a general strike is called and placed into effect. Protests transform into large-scale worker rioting which paralyses Italy, but Mussolini does not want to respond harshly as he fears the king will dismiss him from his position. Extremist elements of the Blackshirt movement (as existed OTL) frustrated by perhaps a butterflied, more indecisive Mussolini stage a coup d'etat and depose Mussolini, leading to Victor Emmanuel III in fright perhaps dismissing most Blackshirt members from their positions in fear of a revolution.
A bloody civil war breaks out between the government and Blackshirts due to mishandling of the situation, confusion and a lack of coordination, with an ultimate Blackshirt defeat but at pyrrhic cost to the government after several months to 1-2 years of fighting. Fascism and the general government becomes deeply unpopular with the people, and war-torn Italy is hit especially hard by either a Great Depression in 1929 or even an earlier one in 1928. With Soviet agitation and aid, an Italian Communist uprising begins as the government responds harshly to worker protests with crackdowns, and the Soviet Union invests more heavily in attempting to co-ordinate some sort of united front for left-wing groups in Italy, perhaps believing it could benefit through:
1. Counterbalancing any possible German imperialism with a friendly, Communist Italy.
2. Putting pressure on France with another left-wing government they share a border with (if the Second Spanish Republic is not butterflied away).
3. A base in the Mediterranean to threaten European operations.
So even if Stalin or someone the likes of him accedes to power and follows a "Socialism in One Country" doctrine of interventionism, it is still very possible to have a Communist Italy arise via Soviet assistance.
Perhaps an interesting prospect could be if Communist exiles from the Soviet Union after Stalin's seizure of power could find a home in Italy after a civil war between the Blackshirts and the Italian government, and assist in organizing the Communist and Socialist movement into something more united. Of course, that would pretty much mean no Soviet aid but the Italian government could fall anyway to a strong enough revolution.