You could also start from Aviles, which is about 15km from Asturias airport. The albergues are then usually around 16-24km from each other, there is some asphalt walking but there is options if you decide on doing it, of going along coastal paths to miss these out or in one case taking a higher level (little used cattle trail from soto de luina to cavedeo), places to jump out would be Ribadeo bus and train links to Santiago and A Coruna, Lourenza and Vilalba, the latter 3 with bus links. This is perhaps my favourite part of the camino del norte and you have the quieter entry into Galicia.
I am also thinking of doing 10-12 days later in the year so I am thinking of the other less populated routes. The Camino de Madrid, the people who do it usually go back and do it again so that says a lot about it. The Portugues Coastal Route, the disadvantage would be the large population areas you would keep walking through, at least with the Madrid you can take 20km out of it by getting a train to the outskirts and starting from there. The Camino Vasco, starts in Irun and either finishes in Santo Domingo de la Calzada or Burgos. Another option is starting at Leon and taking the San Salvador Route to Oviedo 5/6/7 days(120Km) through quiet mountain routes with albergues then continuing up to Aviles (30km) and either finishing in Cudillero or Luarca, both incredibly picturesque fishing villages on the Camino del Norte, there are Feve links to Aviles and to Ferrol from both places.
Mike