I think it would be possible if you picked a "street level" human to start with, yeah, to give you a sense of the overwhelming scale of the universe and battles they're living in the middle of, and if you had a HBO scale budget commitment.

The main thing though is to be really careful to depict the human Imperium as a bad thing.

The game lore has faltered on this lately as an accidental byproduct of making some beginner game packs accessible "good guys vs bad guys", and the side effect has been to suggest that the atrocities they've committed may have been necessary evils, rather than an illustration of its ongoing downfall.

That sounds like splitting hairs, but it’s a really important distinction that could be really easily lost in translation to tv - there are individually good and heroic humans, but the human imperium as it is, is a monstrous, mindless abyss of suspicion and indifference. If you don't get that right, it reads too much like a fascist apologetic - all the intentionally insane in-universe warcrys and mottos etc will just turn into Facebook motivational shit people take deadly seriously.