Not sure why the Death Star should have remained off screen. It’s pretty relevant to the story, and it’s a part of ANH from the opening crawl. If anything, the Death Star in RO was a necessity so that it could have a grand introduction.

Tarkin, however, should have been relegated to cameo status, with Vader as a feared agent of the Empire who will just as soon kill rebel spies as interrogate them. What a cool movie it would have been if the Rebellion’s informants keep disappearing to this shadowy agent of evil, constantly threatening the mission as they barely keep a step ahead.