Having doing the
Camino Frances already, and looking into another one now
Im looking into doing this route - backwards. (There is a method to the madness) - Starting in Astorga, or somewhere there and ending in Sevilla.
You might find it interesting to read this recent thread -
Walking the Via de la Plata in Reverse
Take a look too at Michel Cerdan's
Camino de Piedras - a cultural project involving a walk in reverse from Santiago to Guejar near Granada.
Without exaggerating, the plan that you outlined is much more challenging than the
Camino Frances. Of course, it's not a wilderness hike. There are albergues and way marking. But it's not a gentle introduction to more self-reliant walking, especially the section from Astorga to Granja. Let me explain why:
1. Astorga to Granja de Moreruela is the least frequented stretch of VDLP. Maybe one of the least frequented stretches of Camino in Spain. You will not see much life as you pass through depopulated pueblos, with few cafes and shops, and no other pilgrims. (Most pilgrims follow the Camino Sanabres between Granja and SDC). Unless you're really looking to "mortify the flesh," my advice would be to forget about starting in Astorga. Better to start in Santiago and follow the Sanabres or start in Zamora.
2. After Granja, you will see more life, but the route is still much quieter than the CF, especially when you go "against the flow". You will have daily encounters with pilgrims heading in the opposite direction (short conversations and then goodbye). You will also meet different groups of pilgrims in the albergues in the evenings. If you appreciate a feeling of community, you may feel lonely when you walk the VDLP in reverse. (By contrast, if you walk VDLP with the flow of pilgrims, the sense of community among the few pilgrims on the route is strong).
3. Way marking is not painted with reverse walkers in mind. You'd be wise to bring maps and/or GPS equipment. Most of the stone cubes on the ground should be visible, I guess. But arrows painted on the fence posts and on the reverse sides of roadsigns ... you're not going to see them unless you stick a mirror on your shoulder.
If you're fully on board with these challenges, then you should have an excellent experience. As you can imagine, you will walk ahead of the advancing winter from the north. You could continue from Seville to the coast and winter there ...