By "sedeism" I assume you mean the logical conclusion that one forms based on sound Catholic teaching that currently the Chair of Peter is vacant....
So, no - I will not admit that the Chair of Peter being currently vacant is just "my opinion", rather it is my belief, otherwise, I would not have the conviction to act upon it if it were mere opinion.
Ok, well, you've chosen to make your conclusion your belief, based on what you opine is "the logical conclusion." What you are saying is you've made your opinion a de fide doctrine and you're not only fine with that, you live by it. At least you're not lukewarm.
A pope may make an ecclesiastical law on how to elect his successor, if that law cannot be observed because the mechanism to use for following it no longer exists, then the Church must still have a way to elect a successor to the Seat of Peter in keeping with the Divine Constitution of the Church laid down by Christ. She does and always will.
Well, the popes have made laws mandating how to elect their successors, and to date, that law has only been abrogated by opinions of some priests and lay people. Beyond that, that law is still in effect for all Catholics apparently except for those few.
You keep conflating ecclesiastical laws with Divine laws. On the other hand, it is of Divine law (and ecclesiastical law, cuм Ex, Canon Law, etc.) that heretics do not belong to the Body of the Church.
I'm not conflating anything, you misunderstand what is meant by "Christ and the pope are one head." If it means what you believe it means, then everything popes do, Christ does, ergo, everything Christ does, popes do. But out of necessity to maintain your starting point, you say this does not apply to ecclesiastical law, specifically, this does not apply to the laws on papal elections. Imagine believing this and at the same time, of all things, the papal laws established on the election of popes being mandated with only one head, i.e. without Christ. This is your conclusion on such an important event that will effect the whole Church and hundreds of millions of souls, possibly for many decades is done without Christ?