The issue, it seems to me, is not whether or not any EO have ever been received by baptism. Generally (because I do not want to exclude any instances that may exist) they have not. The issue is whether our Orthodox Faith is determined by the explicit teaching of the most important Fathers, or whether they are to be judged according to our own opinions.
I hate to have to question your intentions, but I am beginning to wonder if you are trying to make me look overly Protestant for the sake of discrediting my arguments. If so, I do not think such an analysis is fair, and I think it has no place in real debate.
I am not seeking to challenge the teachings of the Fathers. If anything I am seeking to question your interpretation of them. Or, if it is true that there is an irregularity in the approach of Saint Timothy and Saint Severus, I am seeking to challenge it in the light of the teachings of the other Fathers. However, I doubt that this latter situation is the case.
You yourself quoted an instance where the Fathers have proscribed that heretics be received by Chrismation. Why should it be any different for the Chalcedonians?
Here is also a quotation from the first rule of Saint Basil the Great:
"Nevertheless, it seemed best to the ancient authorities — those, I mean, who form the party*of Cyprian and our own Firmilian — to class them all under one head, including Cathari and Encratites and Aquarians and Apotactites; because the beginning, true enough, of the separation resulted through a schism, but those who seceded from the Church had not the grace of the Holy Spirit upon them; for the impartation thereof ceased with the interruption of the service. For although the ones who were the first to depart had been ordained by the Fathers and with the imposition of their hands they had obtained the gracious gift of the Spirit, yet after breaking away they became laymen, and had no authority either to baptize or to ordain anyone, nor could they impart the grace of the Spirit to others, after they themselves had forfeited it. Wherefore they bade that those baptized by them should be regarded as baptized by laymen, and that when they came to join the Church they should have to be repurified by the true baptism as prescribed by the Church. Inasmuch, however, as it has seemed best to some of those in the regions of Asia, for the sake of extraordinary concession (or "economy") to the many, to accept their baptism, let it be accepted. As for the case of the Encratites, however, it behooves us to look upon it as a crime, since as though to make themselves unacceptable to the Church they have attempted to anticipate the situation by advocating a baptism of their own; hence they themselves have run counter to their own custom. I deem, therefore, that since there is nothing definitely prescribed as regards them, it was fitting that we should set their baptism aside, and if any of them appears to have left them, he shall be baptized upon joining the Church. If, however, this is to become an obstacle in the general economy (of the Church), we must again adopt the custom and follow the Fathers who economically regulated the affairs of our Church. For I am inclined to suspect that we may by the severity of the proposition actually prevent men from being saved because of their being too indolent in regard to baptism. But if they keep our baptism, let this not deter us. For we are not obliged to return thanks to them, but to serve the Canons with exactitude. But let it be formally stated with every reason that those who join on top of their baptism must at all events be anointed by the faithful, that is to say, and thus be admitted to the Mysteries."
Basil makes it very clear that the Baptism of heretics and schismatics is not recognized as efficacious, and is completed by annointing/laying on of hands. Recognition of their Baptisms can only be a matter of "oconomia". Again, why it should be any different with the Chalcedonians, I don't know.
Also, that St Timothy and St Severus received the Chalcedonians by a confession of faith would not seem necessarily inconsistent with the process described in canon 7 of Constantinople II. For it does say that a confession of faith be received before the converts are anointed with chrism. Whether or not St Timothy or St Severus were advocated just a confession of faith or a confession of faith and then anointing appears to be unknown yet far.