Hi Laurie and Francis
I think it would be a great route through the interior of Portugual, a lot of sierras to go through, long quiet stretches. When I flew into Lisbon last year for my camino I was sat on the east facing side of the plane and was looking in that direction with these thoughts in mind. I am going to see how I feel after the one in May, no more planning for future ones just make the most of this one.
I tried to copy the link to Conrad Stein on my original post,the computer I was on would not let me, that book is the way in. If there is a lot of road stretches, I have feeling they would have come up with alternatives to it, a lot of it is not waymarked. They have updates to November last year on their site, it may be worth contacting your German speaking friends, not only to to find a better translation but also pose some questions on their forums.
What else I would say that if you can find the various walking associations in Portugual it may be worth going on their websites. I went to see my friend in Warsaw last year and we went to a slide show about a Polish couple who had gone to Portugual for a few months and it showed them walking in the interior mountains on various routes and staying in walking club refugios.
It does appeal to me, but I might let some one else do all the leg work first, Laurie?
Buen Caminho
Mike