I honestly think Cavil loves it enough to make the best possible version of what media giant approaching 40k as a series for the mainstream would be.

It is just about how good that is, and if that then captures enough non-40k fans for Amazon to justify the series as an 'Iron Man' moment. I think it has a chance because of how grim the younger public's perception of the future is and how very similar it is to the past where we were much more into the horror and Godzilla vibes at the movies. Where seeing something as dark and grim as 40k will scratch an itch we didn't think of until now.

I'm not sure how easy it will be to work with Games Workshop.

Also, I really would have preferred the Horus Heresy -- which could have a real endgame. Otherwise, 40k could be a series without a point and could be more nimble in it's presentation so that might work better.

I had a hard rule against reading anything where the toy came first, but I've been surprised by HH and 40k. It's not the best writing/storytelling ever, but it is self-consistent and presents such a different view of things I'm enjoying it. They seem to understand what a galaxy wide fight means (it's big!). And the stakes at hand are very high and require obscene efforts from our point of view, but the threat is existential to humanity and it's all justified (?).

“Cavill is a big time fan of <X> geeky thing and so his attachment is a sign that fans should be excited” has a sort of mixed track record at this point. On the other hand, it clearly works for him and I’m sure he’d like to preserve that (note: not trying to call him disingenuous or anything, I think he’s actually a fan of these things but he also clearly plays it up a bit).

So, I’m somewhat hopeful in this case, in the sense that he’s got a producer role from the start and he probably knows that a flop here will hurt his reputation a bit. On the other hand, knocking it out of the park might make him invincible. Also it’s Amazon, right? So it isn’t like there are a bunch of other super prestigious creatives he’ll be butting heads with.

It's a wish that will likely die on the vine. GW will certainly leverage enough influence to see someone in charge who has no idea how to make a production OR they will fight about minutia and it will fail because AMZ doesn't care enough to fight it and don't want to lose it to a competitor. Hence, I expect it to die in pre/production.

There's the draconian amount of control GW has exerted across youtube in recent years, showing their narrow vision. Look at the trail of terrible games and limited CGI media, to see how GW's vision does not scale.