The Room of 40k films, if you will.
Speaking of 40k films, it really strikes me how idiotic people who try to make franchise films must be, that they make things like Ratchet and Clank or Warcraft movies that can't possibly have a good narrative when there are settings like 40k out there. A Triple-A 40K film could be set anywhere in-universe, have a real plot, and not be shit.
It isn't that videogames can't have a good movie. It is that they don't automatically lend themselves to a good script because they lend themselves to interactivity and thus their narratives support that (in spite videogames wanting to be movies nowadays). Comics are a bit better because they are written narratives as narratives and books usually are more about cutting things out.
So a videogame based movie typically needs to create a new story with the material and Hollywood often buys up these properties before they have a good script.
Ratchet and Clank's folly was that it basically was a direct translation of the game's plot shot by shot into a movie.
Warhammer 40k would face the EXACT same problem as all other games... in fact possibly even worse. Since its story is ALL backstory... It has no REAL narrative or story just set pieces. A movie would have to invent a story OR bend over backwards trying to make the backstory into a viable story.
All while needing to overlook the grimdark nature of the setting and how there are no real good guys (Even the God Emporer is basically a baby eating soul sucking Lich)... As well as the fact that the "Heroes" are basically mutants who aren't even human anymore only aping human sympathy with the only emotions they can feel are those that aid them in war.