According to Jonathan Sperber The European Revolutions, 1848-1851 pp221 the French Government of Eugene Cavaignac came within "a hair's breadth of starting a campaign" to support the uprising in Lombardy and Venetia "that could have easily led to a great European war".
This is a situation where the Venetians are more successful and dont make the errors they made such as allowing the Austrians to disperse italian troops and take command of the fleet in Pola manned by Italians sympathetic to Italian Nationalism. venice is thus better led and prepared to resist the Austrians.
A better Venetian account may set Italy alight affecting the actions of the South and Piedmont Savoy. Rallying support across Italy France may be be inclined to intervene.
What if Piedmont Savoy are more determined in their efforts and drive the Austrians from Lombardy and Venetia, let's supposse that France does intervene on the Nationalist side, at this point in History Austria is very vulnerable. Will Austrian defeat in Italy assist the Hungarians.
Russia will presumably act as in OTL to support the Habsburg Monarchy or might a French intervention against Austria give enough impetus to the hopes and ambitions of Polish Nationalist's as to leave Russia with it's hand's full in Poland long enough to delay Russian intervention again, assisting the Hungarian's. Might Hungarian Nationalist's be able to declare and organise an independent Hungary.
Presumably Austrian German Nationalist's support of the Habsburg's will be affected, will fear of the Czech's and war with France drive them closer to the Habsburg's or will an Austrian defeat and increased Italian Nationalist ferment (from victory in N Italy and whatever results this has on firing Italian Nationalism ) fan the fires for German Unification.
Will the Czech's who looked to the Habsburg's be more militant and have greater hopes of independence if Austria and France are at war. And might in the potential maelstrom the Balkan nationalities rise up for freedom from the ottoman Empire earlier.
Does french intervention lead to a "great European war, and if so can this go some way to settling some of the multitude of Nationalist issues that played such a part in bringing World War 1 about long before the Barbed Wire, Machine Guns and Artillery
of the Western front turned war into a static slaughter house.
Regards to all at AHF.