Sorry, I meant your 'explanation' of how to handle my scenario.
Of course, I disagree. In my scenario, what would happen is that the process of canon law would be followed (this is why canon law exists). There would be an inquiry, and evidence of heresy would be presented and the college of cardinals would determine that the pope was not guilty but innocent - and he would remain pope throughout all of this. The italian king, if it was able to be proved that he was involved, would probably be put under an interdict and the evil Cardinals would've been punished in some way as well (maybe excommunication, certainly they would've been banished to a monastery or clerical prison). The rich italian family might been excommunicated until they did satisfactory public penance.
In your explanation, the pope is 'guilty until proven innocent'. I realize you read this in canon law commentary somewhere, and it is applicable in some cases, but a heretic pope is not the same flavor as any other heretic. The papacy is a different situation than any other situation in catholicism.