I don't think there is any difference in the Propers over at least the last 100 years in the Roman Rite. As for the Marriage Ceremony there will be differences as the Local Civil law comes into play, here in England we have to use a certain Civil form rather than the version found in say the 1945 St. Andrew Daily Missal.

As for the rings, certain countries did not have a Tradition for the man to receive a ring, I have certainly seen this part omitted in certain books.

Yeah, only where historical custom comes into play for the ritual and the Mass would there be variance. In England and France using the Sarum/Norman vesture is not unheard of, and the Sarum ritual influenced the way the prayer for the ring was written: to thee do I plight my troth was oddly tacked on to the vows in the USA ritual, whereas it's historically the prayer before the sign of the Cross for the giving of the ring (the English "trads" can correct me on this one). Same for other historically Catholic countries. But it all fits within the post-Tridentine rite, and as tomjaw said, that's pretty standard nowadays.

Those would probably need to go to the PCED through the Ordinary, and even if the Ordinary could do that (which I don't think he can, but at any rate), you'd get a huge blowback from the people who know the difference. Your MC certainly would; what would you do for the altar missal? The priest still has to pray the propers.

I understand the Deus in loco sancto suo vs. Deus Israel bit, but why would you open up the Pandora's box that is choosing readings (especially since the EF mandated readings make much more sense, e.g. it takes a lot of work to apply 1 Cor. 13 to marriage, whereas Ephesians 5 is about it already!)? And how would you pick and choose? The Nova Vulgata and the lectionary based upon it and the Clementine Vulgate and lectionary don't format the verses identically, and the readings are shaped differently, e.g. epistles in the new form tend to cut out "in Christo Iesu Domino nostro" and similar (look at Christmas-it makes the epistle nearly impossible to sing!). So it would be odd to take the books issued by the USCCB for instance which list reading A-B-C, etc. for OT, NT, and the Gospel and then stick them in place in the older liturgy.

Interesting, if only because that’s the reverse of Eph. 5 (marriage is a sign of the church, whereas John 17 is about the church, and so it is also about marriage)

The texts of the Bibles used for the two lectionaries are different. The verse numbering is different; this is a problem in the Old Testament more so than the New. So you’d be mixing the lectionaries in order to do this, and it becomes messy really quickly.

Which communities are licitly using pre-1962 missal and breviary? I always thought that was ... I don't know how to put it, not illegal, but ... unauthorized(?).

Don't get me wrong, I would really like to use pre-1962 (or even pre-1913 for the breviary); I just don't get how it all works canonically.

The FSSP is only partially pre-1962, as far as I know, given that the Nine were expelled from the SSPX over the defense of the pre-Pian liturgy. The IBP is also liturgically similar to the FSSP, at the same time looking forwards and backwards.

Some communities never used 1962. In fact only the French SSPX priests did. The rest used pre-Pian books, while the seminary used 1965. The Latin Mass Society of England and Wales always used pre-Pian, even though the indult followed Tres Abhinc Annos. They have, unfortunately, moved forward at least in some aspects of worship to be in stricter conformity to the 1962 rites.