Minor Austen, mostly executed well (the character intros with the vignettes are very much not for me though).
It would lose all subtlety, but it would almost inarguably be a better movie if Lady Susan was a vampire. It would add so many more levels to the drama surrounding her, Reginald, and Lord Manwaring.
Edit: I did not know Kate Beckinsale plays a vampire warrior in another series until after I wrote this. That was a happy coincidence. Amazing.