For anyone interested in the WH40K universe - and that's a couple of million people worldwide based on book, video game and miniatures sales - they have to have the Ultramarines in it. They're the most iconic of the Space Marine chapters, and the only one to have the word 'marine' in the title IIRC. Calling it 'Blood Ravens' or 'Imperial Fist' sounds too generic.

Games Workshop, who appear to be bankrolling a lot of the project themselves, do seem to be aiming this at the fans primarily and if they pick up some new viewers anyway, than bonus. Over the years Hollywood has looked at WARHAMMER and WH40K several times and given GW a list of demands about things that needs changing to the point where GW just gave up on a serious Hollywood film based on the setting and is now doing their own thing, which is laudable but may backfire horribly.