What Ridley Scott brought to the table was an art-director's viewpoint. I believe it was his call that the world be dystopian rather than utopian. Syd Mead was brought in to realize that vision from Ridley's sketches.
Blade Runner was a magical coming-together of quite a few artists while they were at the height of their careers, Scott, Mead, Ford, Hauer hell, even Vangellis never was better. Blade Runner was Scott's attempt to bring back Film Noir in a sci-fi setting -- something that seems common now, but was a radical breakthrough then.
It's a tough act to follow. And as much as I like Ridley's visual style, his latest films have suffered badly from too much money lavished on sets and effects, and not enough on script and acting.
I can also say that, having read "Man in High Castle", that's not an easy book to put to film. It's a huge, complicated story that's not easy to follow. I just hope that they put the work into making the story work, and not gloss over it just to work in explosions and effects.
I had heard that Ridley was interested in Joe Haldeman's "The Forever War" -- not *that's* a movie I want to see. That book blew my mind, and I really, really, really want a good movie of that.