Well, I'm super excited. Amazon are not traditionally great at adapting with respect, but Cavill is a 40K superfan, and having him in the executive producer seat should really help keep this feeling 'right'. I understand tweaks to suit different mediums, but hopefully this time round it'll do the universe and setting and justice, rather than stealing it and doing something different.
There are plenty of settings and characters it could follow without needing mega budget immediately; the initial announcements do make it sound like this could be a multiple series/film sort of deal also, with Cavill in the 'Feige' seat, ala Marvel, and starring in at least something. Something with an Inquisitor/Adeptus Arbites/Imperial Guard, could certainly start on a more human level, before expanding into more obviously intergalactic territory.
He's said before IIRC he didn't go for Eisenhorn as once you star in a universe, you're that character so he wanted to be careful and get a big enough role. Wonder if he'll go for something like a Primarch, I could kinda see him being playing someone like the Lion, and there are heavy rumours he'll be back for 10th Edition. GW do like tie-ins across the setting with books/new editions so I could see him playing a character like that, as it doesn't get much bigger in Lore (beyond the Emperor), than a Primarch.
Wonder what's going on with the Eisenhorn series too, could potentially all get brought under this umbrella if done well.