I dunno, I could kinda see it - they don’t understand a ton of their own tech, and have folded religious belief into even basic maintenance routines until they can’t tell whether lighting incense or chanting as they work changes the outcome. I don’t know about the admech, but the imperial guard types seem to believe every device from a heavy bolter to an ancient and venerable space marine tank are all equally likely to have machine spirits animating them - presumably they got that thinking from their tech experts. There’s also the sort of outlined belief that tech is sort of… naturally occurring? and that it’s heretical to invent new stuff when the correct process is to discover it somewhere.

Add to that the fact that the quality of their tech has declined pretty drastically from their past (aren’t most STCs, which they basically worship as the best of their modern tech, like the crude, sturdy equipment you’d give a colony that was just starting out?) and the fact that some of it is sometimes possessed by literal daemons or other ancient abominations… it sort of seems like they’re in over their heads compared to the others.

This is great!

I appreciate that a significant portion of the 40k universe’s problems aren’t actually humanity’s fault.

Or paint it red so it can go faster. With enough boyz inside all believing as hard as they can, that thing should be zipping around the galaxy. Don’t have to be sneaky if you’re fast.

A lot of people have used time travel to steal Games Workshop’s IP

I mean, the place is so absurdly big and spans so much time there’s room for variances in procedure and tradition, even inside the same organizations. Especially the inquisition which seems to grant its members an unusual degree of autonomy (from the few books I’ve read that featured them). But even the guard fields a wide variety of regiments with different specializations and ways of doing things. I just sort of assume the mechanicus and administratum and others all see a fair bit of variety, if only because the empire is so huge and poorly coordinated. The variety of tones in different stories is also something I like, for some reason - it seems to help show the scale, I think?

And the ones from trigun

Maybe a chapter serf or an aspirant based on the model?

The solarpunk genre in general might have some good stuff for you - my favorite so far is Murder in the Tool Library, but the Terraformers might be closer to what you’re looking for.

I’ve been hoping whatever he picks to start with/direct is the more straightforward/introductory stuff, because once the shared universe is established, he could play an amazing Caiphias Cain

He’s currently left-handed