Yes, I already looked at Cantica Nova and noticed the same thing. They're actually suggesting that the choice of Preface doesn't matter, anything goes.

Some first examples of what I mean:

Using Biblical citations in the Preface
In Preface VII for Sundays of Ordinary Time, Heb 4:15 is cited. So, one could use it on Sunday 29B, where the second reading is Heb 4:14-16.
Also, Preface VII alludes to 2 Cor 5:14-19.21. So, Sunday 12B comes to mind.
Etc.

I am of two minds when it comes to having the prefaces match the "theme" of the day. In the run up to the Second Gulf War, I saw a priest give a powerful homily on the Sunday of Lent where the Old Testament reading was the giving of the Ten Commandments. His homily was based on "thou shalt not kill" and argued that preemptive strikes were not party of just war theology. Whatever one's view of the situation at the time, I thought was a powerful use of scripture and arguments from established Catholic thought applied to a current world situation. During the homily, I thought it would be an excellent time to use Reconciliation II especially with its preface:

Even more, by your Spirit you move human hearts
that enemies may speak to each other again,
adversaries may join hands,
and peoples seek to meet together.

By the working of your power
it comes about, O Lord,
that hatred is overcome by love,
revenge gives way to forgiveness,
and discord is changed to mutual respect.

(Yes, I know that using that preface instead of the one set for the Lenten Sunday is an abuse. But if that would be the worst abuse I would ever see at a mass . . . )

That said, if we are truly to open up the richness of scriptures, having scriptural references in the prayers which do not relate to a "theme" would seem the better way of doing things. Scripture and salvation are so rich that giving it a weekly "theme" seems reductionist.