The title says all, what if instead of centralizing italy into a unitary kingdom under the house of savoy, the italian monarchy had instead adopted a model close to what the german empire came to be decades later, with each region being ruled by it's royal family but all bowing to the King of savoy?
The main problem that I see with this model is that the italian unification happened before the Prussian one, so it is unlikely that they would adopt that model, but I believe that with a different philosophy in the Risorgimento this could be worked into