One advantage to having the days of the week and the days of the month running on separate cycles is that, over the years, you wind up praying different mysteries of the Rosary for the same liturgical feast. And that can open up the feast in ways you might not expect.
The Solemnity of the Immaculate Conception, for example, strikes me as a natural for the Joyful Mysteries. It's the preface of the Annunciation (which, of course, is the Gospel reading for today), and the reflection of the Nativity (with which it's often confused), and it calls to mind the pious traditions regarding Mary's childhood that prefigure Jesus' youthful visits to the Temple.
Tuesday, though, is the traditional day for praying the Sorrowful Mysteries. Nothing quite rubs the gilt off the frame of a picture of the infant Immaculata like the thought of a sword piercing her heart as a lance pierces her Son's side.
It's all the same story, though. A story of unbelievable extravagance -- too many find it literally unbelievable -- but not a story with extraneous threads. The whole thing is gratuitous and unnecessary, but no one part of it is unneeded to tell the story as God wants it told.
The iconography of the Church -- especially, I suppose, the iconography of Lourdes -- seems to express this. The Immaculate Conception is represented, not as a conception (mercifully), nor even as a newborn (which is about as close to a conception as we'd want to get iconographically), but as Mary herself, perfect in age as well as sinlessness. The expression is not, "This event is the Immaculate Conception," but, "I am the Immaculate Conception."
She who is the Immaculate Conception stands at the foot of the Cross... and, of course, waits in the Upper Room and sits on her throne (as we'll think about next year), and intercedes at Cana and travels the roads of Galilee with her Son (2011).