Most of the folks on this thread believe that heretics remain Catholics, and members of the Church... I think I even saw a post claiming that heretics are formally separated from the Church, but remain materially united to the Church?? More material / formal nonsense...adding gray area to a black and white situation.
The Eastern Orthodox are not members of the Church; yet they possess
material succession. This term is universally used by Catholic theologians to describe the claim of apostolic succession made by the schismatics, so we know that there is such a thing as
material succession. I do think it is very important to make the appropriate distinctions between material vs. formal; and also, designation vs. jurisdiction. In Catholicism, all formal jurisdiction (formal apostolic succession) comes from the Pope; not from a confederation of bishops.
In a scenario such as the one Lastdays described, even if the valid bishops can be found (which according to him, MUST be both sedevacantists AND feeneyites, a rarity indeed, I dot not know of the existence of even ONE!), I do not see a way in which they could claim valid, formal apostolic succession any better than the Orthodox (I am exclusively talking here about apostolicity), who claim they have perpetually nominated bishops to succeed to bishoprics established by the Apostles. However, no Catholic would consider their succession to be formal, but merely material, that is, they occupy the place, but have absolutely no Jurisdiction since Jurisdiction must derive from the Roman Pontiff, whom they reject, (or in the case of the totalist sedevacantist, simply does not exist).