Fr. Tim Finigan over at the Hermeneutic of Continuity blog has posted some remarks from Una Voce regarding the prospect of adding the prefaces from the 1970 Missale Romanum to the Missale of '62 (and added his own commentary as well). You can read that entry here. You may also read Una Voce's prepared report for yourself by going here.
As with many items that come out of the Traditionalist or Neo-Traditionalist circle, the report is a mixed bag. It contains a fair bit of historical information that's fine as far as it goes, but often fails to qualify the position taken as well as thoroughly note the context and contextual complexities that make certain statements less than sure.
The report's argument that the Roman Rite has, traditionally, averred from florid language in favor of restraint is accurate regarding the majority of the recorded Roman tradition. That is, the model of prayer exemplified in the Hadrianum and the other Gregorian sacramentaries became the dominant model without any real competition in Rome. Additionally, the report is correct when noting that the historically dominant tradition in the Roman liturgy also features a limited number of prefaces. To this extent, the report has a sound historical argument. However, the report is conspicuously weak in its use and evaluation of pre-Gregorian liturgical matter.
The Veronese Sacramentary is mentioned as a potential Roman witness that runs contrary to the stream of limited prefaces. Indeed, at times there seems to be a proper preface for every Mass, many Masses having multiple mass-sets. The report, almost dismissively, designates the Veronese Sacramentary as a collection of mass sets from all over Italy. The Veronensis is, correctly, identifies the volume as a collection of Masses and not a proper sacramentary, however, they fail to note the general scholarly consensus that these masses are of the Roman type - as Cyrille Vogel remarks, the mass sets are "authentically Roman (papal) libelli" adapted for the use of the Roman presbyters. To color the Veronensis, then, as a collection of masses from all over Italy is incorrect, if not dishonest. The Veronensis is a collection of genuine pre-Gregorian Roman liturgical materials, papal in origin and reflecting another genus in the Roman liturgical family, one that could represent an older liturgical tradition in Rome.
To say the Roman liturgy has always been one way or another is a tremendous distortion of the evidence we have. It ignores the differences between the liturgy of bishop of Rome, the titular parishes, and even the liturgy of Lateran Basilica itself in addition to textual witnesses like the Veronensis. Granted, the liturgical tradition represented in Gregorian sacramentaries will become the dominant liturgical tradition of Rome, however, the Veronensis and the Gelasianum vetus attest to the possibility of at least three parallel liturgical traditions (transmitted in Latin) in Rome. The Veronensis, as Vogel and others have noted, has a special place for consideration. Although some of its prayers were transmitted down to the Gregorian sacramentaries, much of its contents failed to be retained in the Roman tradition until the revisions of the Missale Romanum. Finally, stating the Veronensis contains mass sets from all over Italy ignores the liturgical diversity of Italy - the Gallican related liturgies of the North, and the Greek liturgies of the South. In other words, there is no contextualization.
The document is correct in stating that the liturgical style of the new prefaces more closely resembles the manner of prayer in the Eastern liturgies as opposed to the Western norm. In this sense, the prefaces of the Missale Romanum (1970) demonstrate a liturgical sensibility entirely foreign to the so-called Tridentine missal and would represent the insertion of an alien element into the old missal. It must be noted that the introduction of the new prefaces would not constitute the first time a practice or tendency of the Eastern liturgies was introduced into the Roman rite. Pope Sergius introduced the Sanctus and the Marian feasts and the so-called Tridentine Missale Romanum hardly represents "Roman usage" but is, rather, Roman with increasing layers of Frankish, Gallican, and German accretions - most of the old missal's treasured Mass sets, Mass formularies, expansive sanctoral and the custom of private Masses are all of Franco-Gallic-German origin.
With the above in mind, it is worth noting that the document demonstrates a degree of inconsistency. The Roman tradition conceived by the authors of the report is not composed of a static Roman tradition, but rather a tradition that regularly accepted direct influence by non-Roman liturgies. Think of it as a Roman substrata with layer upon layer of non-Roman superstrata. Adding the new prefaces to the old missal would continue with the tradition of the pre-conciliar liturgy.