Blade Runner already has a sequel [in book form]. It's terrible, though.
It's not Philip K. Dick 
Would be much cooler if Ridley did Altered Carbon, from Morgan.
The Jeter books are so, so bad. Nothing left to subtlety. And while they're not a sequel to DADoES, they -do- try to marry Blade Runner and the book together, as well as trying to explain a few continuity errors in the movie, IIRC. Every single time Jeter sets up a parallel between the movie or book, he ends up calling out specific attention to, saying,
hey, look, it's a reference to this other thing. That happened. In that movie you saw. I hear Jeter and Dick were friends, but this is not a nice thing to do to a friend's legacy.
And, yeah, I'd rather see Scott do
Altered Carbon.