Suppose then, that all of the Orthodox Patriarchs and all of the Orthodox bishops and their participating theologians, reached an agreement with the Roman Pope. Would it be likely to be rejected by the rest of the Orthodox Church?
No. It happened before and failed, ending in recanting or schism.
I believe you are mistaken there, Shanghaiski. Neither the Council of Florence nor any of the "unions" that happened in subsequent centuries involved all of the Orthodox Patriarchs (much less all of the Orthodox bishops).
I did not explicitly say they did. "All" was understood loosely. My apologies. Okay, so even if all, as in every single living Orthodox bishop and theologian--who are they?--appeared in council and voted on whatever sort of agreement was put on the table leading to full communion, they could still all be wrong if their vote was not in accord with holy tradition. Each bishop, upon his consecration, vows not to make any innovations in the faith, and to uphold the tradition of the Church, that which has been handed down by Christ, his apostles, the holy ecumenical synods, and the saints. I won't go beyond this, being opposed to hypothetical questions in general.
I have to admit that I myself find it to be a rather strange hypothetical.
I'm reminded of Pope John Paul II on the anniversary of one of the "unions". I forget his exact words, but the Orthodox complained that he was making it sound like the Union of Brest could have reunited the two sides but it didn't because of an Orthodox misunderstanding. (My apologies if I'm not expressing the complaint very well.)
If that comment is accurate, it shows just how poorly our Churches understand one another, for we did not reject Brest because we did not understand it, but because it did not bring about a real union, as we see it. Even if the Orthodox were presented with an agreement whereby we had to change nothing of our dogma or practice and accept nothing of the Roman Catholic Church's dogma or practice, only enter into communion, it would still be unacceptable to us, not because we want to create difficulties or even want Rome to drop the last 1,000 years, but because the communion would not be real, we would not be of one mind in the faith. It would also be like pretending we have no real differences, which, frankly, is a philosophy I hear from many who advocate open communion. In our tradition, we have always worked to resolve, not dismiss, the differences we have had with those in schism or heresy. This has happened to varying degrees of success. I respect the desire and the work many have done on both sides, but I think that, often, people enter into religious dialogue as a kind of hobby. Lyons, Florence, and Brest were all rather unbalanced summits with bad terms for us and lots of political pressure on our bishops to conform to their decrees. I think this has has burned our ecclesiastical psyche. For better or worse we look at Roman Catholic proposals with suspicion, often because in what they bill as overtures, we see evidence that they don't understand our position. It has happened so often, we wonder maybe they don't want to understand. We try to state our position clearly, using language which is often blunt and are rebuffed as uncharitable. (I don't say you do this, Peter, I'm speaking only in general, from my observations.) Some things we don't understand, like when the pope dropped the title "Patriarch of the West" in what was billed, at least by the media, as a gesture of reconciliation. But we have never had a problem with that title, which has existed since Rome was Orthodox. In our view, the west is where Rome belongs. So, this as a gesture toward us we find puzzling, for one example.