One of the suggestions doing the rounds about how we can let the 'New Rite' improve the 'Old' is the incorporation of some of the collects from Sanctorale of the new. This is because the collects in the post-Conciliar books refer to the biography or charism of a saint much more closely than do most of the collects in the 'Tridentine' books, and often do so quite neatly.
I don't want to be absolutist and dogmatic on this point. Some of the new collects are indeed fine (I had better make it clear that I am refering to the Latin originals, not the old ICEL parodies). If the two uses of the Roman Rite are to converge and eventually coalesce, I'll put in a vote for S Joseph's new collect: an elegant, slinky, almost Leonine piece of Latinity.
But I would not favour a doctrinaire replacement of all or even many of the old Sanctorale collects by the new biographical ones. My reasons are quite simple: (1) I am in favour of cultural diversity and inclusivity in Liturgy. A rite should not too closely reflect the fashions of any one particular phase in its history. And the preference for 'biographical' collects is a phase, a phashion, and even a phad. (2) The most important thing about the saints is that they are our fellows now; not dead figures in the past with whom the only relationship that we can have is that of recollection and emulation. As the Communicantes and Nobis quoque make clear, we seek the protection of their prayers, and admission into their consortium. And let's be frank about it: even when the facts about a Saint are clear and authentic, it is often far from obvious that we should imitate them. One of the most embarassing sermons I ever heard was by a daft bishop who told a Public School congregation, invoking the example of S Francis, that if their bishop told them to take all their clothes off, they should do so. No: our relationship with the Saints should be that of fellowship, and the old collects of the Roman Rite expressed and emphasised this by their constant requests to God for the help of the prayers of the Saints. That is why it is not even the end of the world if one has to use the collects from the communia from time to time.
Again, I am not going to be absolutist here. But it seems to me that the preference for 'biographical' collects has a lot to do with the exaggerated historicism which led medieval hagiographers, when they couldn't find facts, to elaborate romances. This even tripped up no lesser liturgist than Dr Cranmer. In composing his first (1549) Prayer Book, he was faced with an ancient collect for S Andrew which in effect asked God that the Saint might continue his Apostolic ministry of preaching and ruling by being now our perpetuus intercessor. Poor Protty Cranmer couldn't allow that, so he composed a new collect refering to the Saint's 'sharp and painful death of the crosse'. It was one of the old boy's oops-a-daisy moments; he soon realised (or did one of his hatchet-jawed teutonic mentors waspishly point it out to him?) that S Andrew's cross was an unbiblical legend. So in his 1552 book this had to be replaced with something appropriately biblical about the protoclete.