Taking the second claim first, the claim that the 1928 and 1962 Books of Common Prayer (BCP henceforth) have some absolute liturgical priority due to the Affirmation ignores the fact that its historical context was North America, just as new, questionable liturgies were taking hold in ECUSA and the AC-Canada, at the beginning of the Continuing Church. Which is why those 2 books were said to be the exclusive standard at that time: "No other standard ... exists". Since then the Anglican Catholic Church has become international and other BCPs have joined the authorised list of liturgical resources described as the "Standard of Public Worship" (in Article XIV of the Constitution), such as the Indian and South African, "together with" the Missals. The Missals thus form part of that standard. Indeed, Abp Haverland appeals to them to make the point that receptionism is ruled out by our liturgical formularies considered in full (see p.113 of Anglican Catholic Faith and Practice, Second Edition).
On the other aspects of the BCP vs Missal, Sarum vs Tridentine issue, permit me to quote something I have written before, with new material added:
All Anglican Catholics agree that the BCP was never intended to be a full ceremonial instruction manuali, and that therefore resort must be had to wider and/or earlier Catholic custom to “fill in the gaps”. Supporters of the English use have focussed on what was earlier, and specifically English, and so a genuinely “ancestral” Catholic custom for Anglicans. Supporters of the Roman or Western use have focussed on what is wider and more contemporaneous, and so a living Catholic custom as practised in the Roman Catholic Church. The former are less prone to varying from or adding to the BCP rite in the actual prayers, the latter more so.
There are two related aspects of the English vs Roman use choice, ritual (the words) and ceremonial (the actions).
All the talk about Church architecture, decoration and extra-liturgical devotions that is often brought in is a separate issue in reality, as neither the BCP nor the Missals say anything about these. One could and can find parishes using the missal but with reserved practices in the other areas, and parishes that have BCP Mass but also Benediction at times.
So, if one sticks to the main question, one finds that the argument for English usage (BCP and Percy Dearmer) and against Roman usage (the Missals and Ritual Notes) may be summarised as follows:-
1. Catholics must go by authority in liturgical matters.
2. The BCP and all that its Ornament Rubric implies, as well as its "lack of rejection/overuling of mediaeval ceremonial customs implying permitted/expected retention" are that authority for Anglicans, along with what Bishops command.
3. The Roman Church and its decrees on liturgy are not authoritative for Anglicans.
4. Therefore, the English Rite is obligatory for Anglican Catholics and the Roman rite illicit.
The problem is that we know that insertions of non-BCP ritual material into the post-Reformation English Liturgy were made in the 16th Century from the Roman Missal by Catholic-minded C of E priests, in the 17th Century by Bishops such as Andrewes from personal compositions based on ancient precedents, and in the 18th Century by the Non-Jurors using similar sources. The latter two groups at least are heroes of "PB Catholics", as is early 17th Century Anglican apologist Dean Field, who said the Latin Rite contained nothing in its Missals contrary to sound doctrine. More than 200 years later we had the Evangelical Dean of Canterbury, Henry Wace, saying the same thing. So, the High Churchmen were not as different to the 19th Century Ritualists as has been implied. Even one who largely stuck to the Prayer Book, Bp Overall, did so by re-appending the prayer of oblation and thanksgiving to the Consecration prayer, showing that he was not enamoured of the then-contemporaneous (and authoritative!) English BCP Rite unaltered. And, in fact, it was successfully argued long ago (1685!) in a legal context that additions to the BCP service that did not substitute for it were permissible.
An extraordinary oversight by those opposing as illicit additions to the BCP rite which are not covered by any rubric is consideration of the history of hymnody in the Church of England. At first hymns were inserted into the liturgy by Low Church clergy for what can fairly be called evangelical reasons. This was frowned upon by authority but not stamped out. Indeed, by the beginning of the 19th Century, even the “frowns” were disappearing. Nevertheless, while the use of hymns in Holy Communion increased and became generally accepted during the 19th Century, it was not until 1890 that the Lincoln Judgement officially “allowed the use of hymns provided they did not interrupt the course of the service” (The Oxford Dictionary of the Christian Church, Third Edition, p. 811). And there was still no rubrical permission at all within the BCP liturgy itself for these additions, which are undeniably the addition of extra public prayers. These hymns are the source of the Sarum-based additions defenders of the English Rite inserted, including the Introit, Gradual, Offertory and Communion sentences. Now, if such additions to the authorised public prayers were accepted by all, based on a common-sense understanding of the need for enrichment of the service and a resultant developing custom, how much more must Missal additions of non-public prayers be justifiable? After all, the forbidding of unauthorised prayer seen in, for example, Elizabethan legislation -- “all Ministers shall be bound to ... use ... all ... Common and Open Prayer, in such Order and Form as is mentioned in the said Book ... and None other or otherwise” [emphasis added] – clearly does not apply to personal prayers of the Celebrant not said to be audible to the people, but just as clearly does apply to all those hymns and other public services or rituals additional to the BCP which either Evangelicals or “Prayer Book Catholics” of the English Rite have accepted happily. Therefore, if anything, the Missal approach had less of an “authority problem” than the alternatives, especially given that Low Church Anglicans had often illegally varied from the rite, including by deletion, for a long time before the Ritualists came along. But, in fact, the forbidding abovementioned was never taken absolutely literally or applied consistently by the Church of England, and High Church Anglicans always understood Catholic tradition to have priority.
Therefore, at the very least, Missals which take the BCP rites and add to them from the Latin rite are following Anglican precedents in principle and not breaking any Church laws, especially since most of what is added consists of private prayers of the priest said in the low voice. (In other words, when I say the Mass according to the Anglican Missal 1549 Canon option, I am being a faithful Anglican Catholic.) If there are plausible arguments that the introduction of the BCPs and quashing of the old rites were not done in a completely canonically regular manner, which there are, then even the "BCP must not be contradicted in any way" principle need not be considered sacrosanct. (That means if I wanted to use the Gelasian Canon translated into English in the Missal instead of the 1549 BCP Canon, I need feel no discomfort. However, I prefer the 1549.)
As for the rulings of bishops, which naughty Ritualists are supposed to have ignored to their own condemnation as congregationalists, the following facts should be noted. Many 19th and 20th Century bishops tried to stop anything looking Catholic, even those things mandated by the Ornaments Rubric, and they made no distinction between English and Roman ritualism. Anybody who supported Eucharistic Vestments, Candles, Incense, etc., was the enemy. By the time such unjustified and uncanonical persecution ceased, the bishops who were happy for all these Catholic customs to be re-introduced also made little distinction between the Rites in the main, as I understand it. So the episcopal jus liturgicum was to begin with largely irrelevant to the choice between Rites because unlawfully anti-BCP, and irrelevant to the choice later because by then many bishops were either permitting the Roman usages (being by then well-established customs) or turning a blind-eye to them.
Therefore, the claim that the BCP rite and its explicit and implicit [i.e., neo-Sarum, Ornaments Rubric-based] ceremonial cannot be touched or enriched without being unAnglican and unCatholic is false. Once tradition, law and reason are taken into account, the authorities mentioned in point 2 above are seen to be important but relative, not absolute.
The question then becomes "but is the Latin Liturgy after Trent in any way appropriate or authoritative as a source for Anglicans?" The answer is "Yes" for three reasons. One, the RCC is our main sister Church in the West, to whom we are in many ways closer liturgically and culturally (at least with respect to their Latin Rite) than to the EOC, so its practices provide a relevant, easily accessible and useful precedent. Even the Old Catholics with whom we were in communion used the Tridentine rite. Two, common-sense reference to such a handy precendent is NOT equivalent to claiming that this option MUST be taken simply because it has Papal backing. So, the fear that using the Tridentine Rite for supplementary or alternative material is the same as uncritically accepting the absolute monarchy of the Pope is an unreasonable one. Three, even the cleverest arguments by pro-English Rite apologists cannot hide the fact that when it came to determining how we should "clothe" the BCP liturgy when that need became more apparent and pressing in the 19th Century there was a lack of binding, explicit and unambiguous instruction within Anglicanism that answered that question in detail. The Ornaments Rubric implies the tools to be used, but not how to use them. And the pre-Reformation English ceremonial said to have implicit authority (at most) had in fact been in desuetude for centuries, and had perhaps never been actually used by anybody with the 1662 rite until then. With such an authority vacuum, once the convenient Roman option had been established, and then become customary and eventually explicitly permitted in places, any later attempt to paint this option as merely rebellious has to be seen as illegitimate. Basically, Anglican Catholics of the 19th Century had a choice between: painstaking historical reconstruction of old, native ceremonial to be re-inserted as much as appropriate into an (almost) unchanged BCP rite in a way that quite possibly had never been done before, but which could be rationally defended on the basis that the loss of ceremonial had never been necessary or mandated and so remained a valid source; or quick reference to the most closely related living rite of the time, but one which had diverged a bit from the native precursors, in order to use both ceremonial and extra non-public prayers. Either could be defended as according with respect for Catholic custom and common-sense.
Finally, this is largely an argument about nothing. Most Prayer Book Catholics are content to follow their traditions and let Missal users follow theirs without interference, and the feeling is mutual, even within the ACC. The differences in ceremonial are not very great since both "The Parson's Handbook" and "Ritual Notes" allow use of incense, the mixed chalice, Vestments, Frontals, Candles, crossings, etc., etc. The differences in the prayers used are somewhat greater but irrelevant, since the pre-Tridentine English Rites (e.g., Sarum) were not that different to the Tridentine rite, and, as mentioned above, the insertions from these and other sources had been made long before Tractarians or Ritualists existed and such insertions were never condemned by lawful authority but instead sometimes used by respected bishops! More importantly, both English and Western/Roman rites within Anglican Catholicism are almost 100% BCP when it comes to the “Common” prayers anyway, if the Gelasian Canon is not used. In some parts of the liturgy, where Missal usage could be justly criticised for unnecessary duplication of supplications or thanksgivings already covered by BCP material, the Anglican Missal makes explicit the optional nature of the Missal addition for just this reason, e.g., the rubric before Domine Jesu Christi, Fili Dei vivi. Indeed The People's Anglican Missal, in speaking of the prayers additional to the BCP said by the priest in a low voice, states on page 256: “The worshipper may profitably recite these devotions even if the Celebrant omits them ... no Rubric requires their use”. Therefore, it must be remembered that Missal additions to the BCP rite are intentionally given as optional, not mandatory.
These are just some of the reasons why I have followed both traditions at different times and felt comfortable with both. There is no need to pronounce against those who use a tradition you don't prefer, as both have a defensible place within the greater tradition, and both are used to worship God in reverence and truth and to edify the people of God.