Let's recap.
Bellarmine and many others cite two different heresy scenarios in which a Pope might lose office, one in which he's manifest and loses office ipso facto and the other in which the Church would judge him a heretic.
What hasn't been established is what kinds of scenarios would fall in either category. Siscoe and Salza based their entire argument on the entirely-gratuitous assertion that only apostasy falls within the first category.
This is categorically denied by all the Canonists who dealt with the subject of tacit resignation of office; these Canonists, whom S&S fail to cite in their lengthy tome, categorically DENY this assertion, stating that both apostasy AND heresy fall into the category whereby there would be tacit loss of office. Cardinal Billot further confirms this in his commentary on the Pope St. Clement vs. Nestorius situation, stating that Nestorius had lost episcopal jurisdiction from the time that he began preaching his heresy, and not merely at his formal condemnation 3 years later. While commenting on Canon 188, S&S claim that only apostasy falls under this category, whereas all the trained Canonists commenting on the passage agree that both heresy AND apostasy do, with there being a dispute only about whether "pure" schism qualifies.
S&S claim that Popes can be subjected to a discretionary judgment, and that this is an exception to the rule that the Pope can be judged by no one. But, in point of fact, discretionary judgement has as its object not the Pope himself, but, as Torquemada explains, the truth of a proposition, in the case, the proposition that a given heretical Pope is in fact not a Catholic. Pope Innocent III explains this type of judgment as, rather, meaning to "show that [the heretical pope] has ALREADY BEEN judged." So it's SHOWING or AVERRING the a priori fact that the man has suffered loss of office.
Finally, we are left with nothing but a gratuitous assertion that a pope who retains his authority cannot dissolve a General Council. It is Church dogma that the Pope has absolutely supreme authority over Councils, and Lateran V explicitly teaches that the Pope has the right to dissolve Councils. PC2 dodged this question by merely dismissing it as "overcomplicating" the situation, whereas in fact understanding how this can be is at the very heart of the dispute.
We must state that such a one who is incapable of dissolving the Council is already in a state where he's no longer Pope simpliciter, since any such Pope COULD in fact dissolve a Council, for the Church teaches that his power is "absolute", i.e. cannot be limited. This question must be answered, and cannot simply be dodged. By the mere fact that a Council is in the process of determining whether he's actually the Pope, he's at that point in the category of papa dubius, which a number of theologians classify as being tantamount to papa nullus. In other words, it's by virtue of his papa dubius, papa nullus status that he is incapable of dissolving the Council. In other words, it is NOT because the Pope's authority has been "limited" but rather because he's in a state of being a papa nullus. As papa nullus, he would, according to these theologians, not have the papal authority.
Let us consider such a Council. As soon as it begins, the putative Pope dissolves the Council. Then the Council reaffirms that he is in fact Pope. That means that the dissolution of the Council was legitimate, and the Council was in fact dissolved quoad se. But if the Council concludes that he was in fact a heretic, then his dissolution meant nothing, since he was no longer pope.
Papa Dubius exists only in the realm of quoad nos. In terms of quoad se, he either IS the Pope or he is NOT the Pope. This relationship between the quoad se and the quoad nos needs to be further explored.
We had one situation historically where there was a legitimate pope quoad se who was hauled off and jailed, and another elected and universally accepted, to the point that there was a different pope quoad nos. This seems to blow away "convalidation" theory.
If there's an existing legitimately elected Pope, the subsequent universal acceptance of another cannot depose the man and override the fact that he is pope quoad se. Cardinal Siri thesis anyone?