You can't do this with the Pope in Rome. Maybe the Popes could be kept in Avignon, making the Italians resentful.
What Emperor Julian (oh the irony!

) said.
It isn't ASB in and of itself, but in the OTL setup, I can't see how it could be done. Maybe if the whole "I'm the pope", "No, I'm the pope!", "You two are wrong; I'm the pope"-thing had lasted longer than it had, enough people would eventually get fed up with the ridiculousness of it all, and more people would be responsive to Luther's points.
I'm also thinking that it might require a sense of nationality that Italy simply didn't have at the moment. No, I'm of course not saying that the rise of nationalism came 300 years earlier than what is commonly accepted. But part of the complaints in Germany at the time, was Germans working their asses off being "bled" to fund the luxury and projects of churches elsewhere. Italy got rich off Germany, by working the system, and OTL, Italy doesn't have much reason to go protestant.
True, the leaders of the merchant republics might see a way to strengthen their own position like the German princes did, but unlike the German princes (and not all of those, mind you!), they would not have the popular backing needed, not to mention that the RC church was considerably more powerful in Italy than in Germany, where it was powerful enough already.