So, here are my casting ideas for the two lead roles.
As the renegade cop/fighter pilot/vampire slayer who heads the U.S. resistance to the vampire invasion: Will Smith, of course.
As the king of the Vampire Nation: Hrithik Roshan.
The film will be like Dhoom 2 in that Hrithik will nominally be the bad guy but will really be totally awesome. (And he'll make an infinitely better-looking vampire than that other dude in that one film). Then in the end it'll turn to all have been a big misunderstanding between the United States and the Vampire Nation, and he and Will Smith will ride off on a motorcycle singing "Yeh Dosti" together.
Yep, this movie will be fabulous.