OK.
Italy had 12 ironclads averaging about 4,000 tons.
France had 17 averaging 6,000 tons, plus 9 armored coast defense ships and 8 armored cruising ships that were about equal to the Italian ironclads.
The French fleet was also much superior in training, logistical support, etc.
Given the poximity of Corsica to French bases, the situation in France would have to be pretty chaotic for Italy to get away with this. This would probably also make Italy a giant target for French revanchism, since France can actually beat Italy.
I wonder at the effect upon colonialism? The scramble for Africa was partially started by Leopold, but in no small way also because of the desire of the French to regain lost pride by building a large colonial empire, causing the British to respond by expanding as well. If French energies become directed at Italy, you might see a totally different Africa, certainly including expanded Ottoman/Egyptian influence, which was growing steadily at this time, and we might see less French attention in Egypt and the Ottoman Empire with drastic results.