OK, here's a thought for a dull afternoon. Due to your incredible screenwriting abilities and clout in Hollywood, as well as your fanatical love of Dark Heresy, you are called into the offices of a top Movie Mogul
Sitting opposite you, gazing across the expanse of his vast, shiny desk, puffing on a cigar and playing idly with an executive toy, he instructs you to make the opening movie in a 3-part trilogy set entirely within the Imperium of man, the first of an epic Warhammer 40k series. He tells you that you have a budget of $200 million (for special effects, stars etc) and that if the film makes over $500 million, you'll get 5% of the gross profits. And get to direct the sequels.
As you stagger home, dazed by the awesome responsibility on your shoulders, your mouth dry at the thought of finally having the funds to buy an original DH Collector's edition on ebay, you slowly start to wonder about how you'd go about it...
What would you feature in the screenplay? What's the plot?
How would you explain the incredibly complex Imperium to total novices using a practically infinite budget?
What action/set pieces would you employ?
What stars do you cast, if any?
What do you save for the sequels?
How do you avoid either the movie or the trilogy sucking completely?
Any thoughts?

