I think you're overestimating Italy's ability to contribute to a Prussian victory and the Prussian military itself.
I'll take breech-loading rifles over muzzle-loaders any day. I'll grant that Italy's main contribution was to keep the Austrians from being able to concentrate their forces against Prussia. However, Austria was in no shape economically to fight a long war over keeping Venetia and the German Confederation. The best Austria could hope for out of winning Könätz is either better terms that what the Peace of Prague provided after such a short war where the Austrians had so consistently done so poorly against the Prussians or another major power entering on their side. Problem is, no major power was inclined to do so.