This is something I've been thinking about for the past several months or so, and I've decided to finally put it in print.
I have two ideas in mind. For the first, the basis would be the pre-Pius X Roman Missal.That would be the pre-supposed text. To it, the following reforms would be made for the missal:
-The suppression of the private recitation of the choir's parts
-The addition of 'et omissione' in the confiteor
-The addition of a second reading between the gradual and alleluia on Doubles of the II class and above.
-Addition of prefaces for the Sundays and weekdays of Advent and Lent
-Addition of prefaces of the Blessed Sacrament, of proper feasts of the Lord and Our Lady,all solemnities of the kalendar, the dedication of churches, and the commons of the saints.
-Option of the audible recitation of the canon at low mass.
-after the prayers before communion, the celebrant proceeds to the ecce and makes his communion.
-Option of communion in both kinds
-Optional use of the vernacular for the readings and proper prayers
For the Kalendar:
-The suppression of the rank of 'simple'
-The raising of simple octaves in the universal calendar to common octaves
-The preference of the Sunday mass (Out of Advent and Lent) over those of feasts,except for feasts of the Lord, Our Lady, and saints with a special significance to a place.
This isn't too radical. My other proposition however, relies on the new missal, and the many reforms would be thus:
-Penitential act at the foot of the altar, facing it.
-Restoration of the antiphon and versicles before the confiteor (But not the psalm) and the absolution.
-Mandatory recitation of the celebrant's private prayers in Latin rather than the vernacular.
-Addition of the prayers Aufer a nobis and Oramus te.
-Collects sung or recited at the altar rather than the chair (except in pontifical masses.)
-Restoration of the full prayer Munda cor meum.
-Genuflection at Et incarnatus est at all seasons of the year.
-Option of the prayers Suscipe sancte Pater and Offerimus tibi.
-Cleaning up of the modern offertory prayers.
-Restoration of the full prayer Deus, qui humane substantiae, and the addition of the prayers Veni, sanctificator and Suscipe sancta Trinitas.
-Part of the canon said quietly while the santus/benedictus is sung at high masses, the rest aloud.
-Restoration of the celebrant's prayers before communion.
-Mandatory recitation of the Placeat tibi.
And in the kalendar:
-Restoration of all vigils and octaves
-Restoration of Septuagesimatide and Passiontide
-Mandatory celebration of moveable feasts on the actual day, with option for an external solemnity on the nearest Sunday.
-The addition of 'Post Epiphaniam' and 'Post Pentecosten' after 'Per annum' for ordinary Sundays.
-Restoration of the lenten feasts of the passion and the Seven Dolours, and the feasts of the Chair of St.Peter at Rome, the Precious Blood, The Invention of the Holy Cross, the Patronages of Ss.Joseph and Michael, St.John at the Latin Gate,St.Peter in Chains,and the Holy Maccabees.
With everything else staying the same, except that the rubrics for the manaul actions of the celebrant would be taken from the older missal, rather than the vague ambiguities of the new missal. In any case,the principles are that the kalendar and the priest's prayers at the order of mass shoule be identical between the two. Some concessions of options have been made, because they can make the mass easier to understand without reducing it to the simplistic celebrations we see today.The idea is that the two missals should not be so radically different from each other as to almost form different rites in and of themselves, but rather, with some differences, they should present the Roman Rite as it stood before the many unfortunate reforms of the 2oth century. This includes texts, rubrics, ceremonies and even language and music, where applicable. Eventually,when I get the time, I'll type out an order of mass so that you can get a better understanding of what I'm getting at.