I am interested in walking from Arles to Santiago de Compostela via Beziers, Carcassonne, Montsegur, Foix and then across to Lourdes. I am very interested in visiting some of the key Cathar regions inspired by some research I did for a book I recently wrote. Is this walkable and would it be recognised as a part of the pilgrimage to Santiago? Are you aware of anyone who has walked this path or can you recommend a book?
Seems that what you're aiming at looks like the "Voie du Piémont", a trails that starts on the mediterranean coast and reaches St Jean Pied de Port, along the North side of the Pyrenees. There's a website, in French, dedicated to this trail (http://vppyr.free.fr/vpp.php3) and to alternate trails towards Spain.
There are also marked trails (GR's) exploring various historical places in connection with the Cathars. A few examples (in French again, but maps are self-explanatory!):
. GR107: http://www.ffrandonnee.fr/boutique/topo … g&v=15
. GR36: http://auderando.fr/sentiers/s_gr36.php
Going from the Arles route to Béziers or Narbonne, you could walk along the Canal du Midi from le Seuil de Naurouze / Montferrand. It's easy and straight forward. And also very beautiful.
Recognised as a part of the pilgrimage to Santiago? Yes definitely. Historically, pilgrims were heading from everywhere, taking any trails to reach Santiago. So, why not the way you're planning? If you ask whether you'll get the Compostela once in Santiago, only the last 100kms by foot in Galicia are required.