Talking with Gianni Caputa yesterday, on the way back from Nazareth, I learnt that von Balthasar was a disciple of Henri de Lubac. I know that de Lubac was himself influenced very deeply by Pierre Rousselot, whose unpublished work he edited for publication. See my paper, Tradition and Innovation in Christianity.
I was wondering about the connection between de Lubac and Blondel. A cursory search of the net throws up a book that i actually have, though in Nashik: Antonio Russo, Henri de Lubac: teologia e dogma nella storia. L'influsso di Blondel.
On the other hand, it might be interesting to explore De Smet's roots in Pierre Scheuer and Joseph Marechal.