Hi, Robert,
I have been in Lamego, and it's a nice town very close to the Douro River and its valley, so any camino that passes through there would have some amazing scenery. I didn't know there was a route through that part. I do know that some walkers leave the Vdlp in Zamora and head up through Braganca, but my hazy sense of the geography suggests that these must be different routes.
If there is a route from Coimbra to Chaves, my guess is that there are no arrows. From Chaves, I bet you would connect with the Vdlp in Verin (actually, this is a variant of the Vdlp, but it rejoins the main Vdlp in Ourense, I think). Sounds complicated but like a great adventure.
But what I suggest is that you contact the
http://www.vialusitana.org and ask them. On their web page, there are several email addresses listed, with the flags to indicate which languages they speak. Helena is the go-to person for English speakers, though in my experience they all speak great English.
Good luck with this, keep us informed through the forum, because lots of us camino addicts eagerly await news of new ways to walk to Santiago. Bom caminho, Laurie