I really think they should start small, a lower budget intro series based on a hive world, a warhammer crime series, following arbites leading investigations in x and y, and from there expand the world, introduce the inquisition, and so on and so forth. They just need a damn good story, that happens to be set on a hive world, rather than a 40k universe that the writer know **** all about writing. This has been the main issue with the LOTR prequel series, it just wasn't very well written, same with a great many other series which have failed recently.
Andor worked as it could have been in any universe, anywhere, the expanse was the same, they worked due to good story.
Use that set it in the universe, pull people in, then start multiple projects and offshoots exploring different parts of the universe.