In hindsight, lowering most newer duplexes to semiduplexes (ensuring Sunday Commemoration) would have been fine to elevate Sunday. (Long prime could have been restored if ferias are not said) It also helps with the Scriptural lessons, as semiduplexes are read from occuring scripture, instead of the Common, but this is moot in DA. It was also a generally good idea that feasts hitherto assigned to Sundays were given fixed dates. Arguably, it went a bit too far, as now almost every Sunday is green. Also, some feasts deserve to be on a Sunday, for example, Most Precious Blood. It also would be nice to see October where Sundays were impeded for the month of the Rosary, or something like that. Major duplexes and older duplexes should still get the priviledge of impeding Sunday.
Some semiduplexes could also be lowered to simplex, and, if needed, a mere Commemoration. Though this seems a bit too far, but these seems to be an underutilized aspect of the Breviary. Are we really slighting a saint if they are placed as a Commemoration? Rather, it is an honor already, being in the Martyrology is already quite significant!
To solve the problem of too many semiduplexes (or nine-lesson feasts in general), I think a optional semiduplexes (minor semiduplex? semisemiduplex?) would be required. Using this, a cleric could either choose to say the optional feast (with 9 psalms) or the feria with a Commemoration of the saint at Lauds and Vespers. This way the Psalter schema is untouched. Another idea could be that for these lower-ranked nine-lesson feasts, the DA schema be used, thus keeping ferial days longer.
A new major simplex rank (a la pre-Trident of 9 psalms and 3 lessons of the Saint), while traditional in some aspects, makes no sense in the context of semiduplexes, having the only differences of having fewer lessons, Parvum obligation, and no transfer rights. Unfortunately, they do not make much sense except in DA, as some hybrid between a major duplex (which are proper) and a simplex. If this were implemented in the Roman kalendar, then it would quickly become the main rank, being the easiest to say. Then again, it could be tried experimentally for those who are busy.
As for Advent and Lent, there should be a middle ground between Commemoration (simplex and third class) and duplex. Perhaps (lower-ranked) 9 lessons feasts gets downgraded to simplex with 3rd lesson?
I like the 1967 concession where on first and second class feasts, only one nocturne needs to be said. Not exactly that, but a concession where, if celebrated publicly, for nine-lesson feasts, one nocturne would satisfy the obligation. For Sundays, the first 3, 6, or 9 psalms could also suffice.
I also like the 1970 concession where Matins can be said in between any hour. Of course, I would also allow anticipation of it (with Lauds) after 2pm the previous day, and in the Breviary, it would retain its placement.
Additionally I would like the choice for clerics to choose between Roman, DA (not 62), (a re-worked) LoTH and Anglican schema. The last two would be on an experimental basis, depending on how traditional the LoTH turns out to be and how well the Anglican schema works for the univeral church. (It is very simple, maybe too much so, but is a better 4 week schema than LoTH) Also, the Monastic Breviary could be allowed, but personally I have never prayed it nor do I like the idea of it (for secular clerics).
I very much like 118 said every rather than the hodgepodge of DA, but the Gradual psalms could be substituted, as it is now in the LoTH and Monastic. As for the Canticles, it seems like the new (Old Testament) ones are here to stay, but I would rather them be excised (The New Testament Canticles are uncalled for). (This isn't the Mozarabic rite, which also has a New Testament Canticle, and too many Old Testament Canticles)
Separately, on the topic of Votive Offices, DA made it such that it would make almost no difference if these were said ad libitum or not. They actually integrate quite nicely to DA, maybe as a concession for those who want a more varied Parvum.
On Parvum, it could be tried that some clerics recite it in lieu of the full office, perhaps with additional obligations of Defunctorum, Gradual and Penitential Psalms. It wouldn't be the worst idea to have them pray Hours of the Cross and Holy Spirit as well. (Plus Votive from earlier, or even the proposed major simplex)
Nova Vulgata will be tolerated. Quinonez should not be brought back. Prime should obviously be brought back, but it is a bit bothersome to have a separate book for it. Maybe integrate the Martyrology into the Breviary, a la de Bute, as the Breviary is already several volumes. 1967 concession of dropping absolution and blessings should not be given.
A Few Other Things:
On Confirmation, I think that young people leaving the faith is in no small part affected by them not being sealed with the Holy Spirit. It changes your soul, and I can personally attest to it.
As for the 1917 Code, I can't fault St Pius X and canonists for wanting a new, coherent code that followed modern principles. Sure, it has some novelties, but a new standard and consolidation cannot be blamed.
As for Modernism, the essay "The Pre-Conciliar Church" has the best take I have read.