RandV
It's a wolf v2.0
the valyrians freehold from its peak, leading into the doom would be very interesting. only issue would be that the valyrians speak valyrian and this universe already introduced us to characters speaking that language albeit in small segments. would they speak english if a show was entirely based on valyria?
I don't know, Valyria is a bit more of the exotic fantasy variety, and GRRM's work isn't really about that. It's more the characters that are interesting than the world building. And if you want that type of TV show then the good news is Amazon Prime is making Robert Jordan/Brandon Sanderson's The Wheel of Time series.
With the multiple TV series they have planned maybe they'll get to Valyria but I think they have the right idea here sticking in Westeros for the first one and focusing on the Long Night.