The Mass of the modern Roman Rite could do with some enrichment from its Traditional forerunner.
Most of the suggestions I am about to make simply give the priest a few more short private prayers to say, to help him in his focus and devotion at the altar – for, if the celebrant be devout, this will conduce to edify the laity.
One very simple and small addition would be, when the priest communicates himself, when he says Corpus / Sanguis Christi custodiat me in vitam æternam, he preface each aspiration with the traditional psalm-verses appointed for this purpose in the all the editions of the Roman Missal down to 1962: before receiving the Host, Panem cælestem accipiam, et nomen Domini invocabo; before drinking from the chalice, Quid retribuam Domino pro omnibus quæ retribuit mihi? Calicem salutaris accipiam, et nomen Domini invocabo. ("I will take the bread of heaven and call upon the name of the Lord"; "What shall I render to the Lord for all that he has rendered to me? I will take the chalice of salvation and call upon the name of the Lord" – Psalm 115:12-13, replacing "chalice of salvation" with "bread of heaven" in the first case.) This is a gracious and delightful meditation.
A second improvement: at present, when performing the ablutions, the prayer Quod ore sumpsimus is to be said; why not provide Corpus tuum, Domine, its traditional partner, as an alternative, just as is done in the Novus Ordo with the two prayers before communion? Some could conceivably object that the Quod ore is in the plural, while the Corpus tuum is in the singular – but in fact this better accords with the two alternative prayers before communion, Domine Jesu Christe and Perceptio Corporis, since they are both in the singular.
Ought, say, the Veni sanctificator be restored at the offertory, or "preparation of the gifts" as it is called nowadays? I would argue not, since the new Eucharistic Prayers all have explicit epicleses, which more than substitute for this prayer. However, something simply must be done about those dreadful Bugnini twins, "Blessed are you, Lord, God of all creation..." – to replace them with some of the many far more devout mediæval offertory prayers would be greatly to be desired. Certainly, in respect of the chalice, the Offerimus tibi is almost exactly the same length as Benedictus es, Domine... vinum... (65 as against 62 syllables – and if the Amen of the former is made a response, it actually comes in as shorter than the latter with its optional response Benedictus Deus in sæcula, "Blessed be God for ever").
Why not mandate that the priest say privately as he approaches the holy table, "I will go in to the altar of God, to God who gives joy to my youth"? This small but significant addition would surely help him to focus on what he is doing and the high mysteries he is about to celebrate.
It ought be encouraged that the traditional vesting prayers be said by the priest; and likewise, as was the mediæval custom, that as part of his prayerful preparation – which Canon Law mandates; one wonders how many priests observe this rule! – or even as he goes to the altar, he could pray Psalm 42. The Missal ought provide Psalm 42 among its selection of prayers for use before and after Mass; similarly, it ought provide the text of the Last Gospel, St John i, 1-14, In principio, as a devout passage warmly commended to be said after leaving the altar. Our Catholic forebears were so taken with these prayers, one a psalm, the other a Gospel pericope, that insensibly over many generations they came to become de rigueur for use at Mass: surely their devotional value is not spent?