Italian’s adventures happened in a precise scenario...
With Elizabeth of York married in Naples and the absence of tension between Naples and Milan caused by the strained relationship between Alfonso of Aragon and Ludovico Sforza (who will not be present or relevant with the annulment of the wedding between Gian Galeazzo and Isabella) is unlikely who France will be able to go in Italy...
Now you have no tension between Milan and Naples and a France who need to be careful because the tension between them on one side and Austria-Burgundy, England-Brittany and Spain on the other. Add to that the fact who in OTL during the Italian adventures France was allied with Spain (at least before the effective conquest of the Kingdom of Naples) while here relationship with Spain are strained because Charles is fighting against them as King (Consort) of Navarre while England has a big interest in Naples and Ludovico Sforza no reason for searching allies against Naples...
While the Italian Wars are likely butterflied, a war over something is likely to break out before too long. Where it will be however, I'm not sure. There'll very likely be a war over Edward V's marriage to Brittany, I'm sure of that much. As a side note, trade with Naples will probably be good for England.
I'm not sure I follow the argumentation as to why the Habsburgs converting is a terrible idea. I agree it's very risky, but the argument seems to be that conversion severely jeopardizes Habsburg interests in Italy, Hungary, and Bohemia. However, the Italian Wars probably won't happen ITTL, Janos Corvinus is relatively secure as king of Hungary and probably has a son by this point. If Charles V marries the Bohemian heiress, this complicates matters, as Bohemia is divided into Hussite and Catholic factions*; whether or not the Emperor converts, one faction will be angered.
*At least I think this is how things worked in Bohemia at this point. I've also heard Matthias was ruler of Catholic Bohemia, while Vladislaus ruled the Hussites, or a mix of Catholics and Hussites. Can someone please explain this?