So, this is for the fan casting contest being held here, but these are also my honest opinions. When reading all 6 books, these are who I had in mind.
First recast: Hailee Seinfeld as Rosemarie Hathaway.
While I think the actress who played her was brilliant, this person would play a much better Rose. She's feisty, and you have to be to fill out those shoes!
Second recast Sebastian Stan as Dmitri Belikov
This guy has it all. Acting experience, good looks, the right accent, and he's already played a badass character in the winter soldier. Score!
Third recast: Evanna lynch as Vasilissa dragomir
This lady has already proved she can pull of being a little weird, so a playing a vampire princess would be no sweat. Cheers to Luna!
Third recast: Steven Straitt as Cristian Ozera
This guy has already played a firestarter once, so Cristian would be no sweat! Bonus points because we'd be reuniting Sebastian and Steven!
Forth recast: Bill nighy as Victor Dashkov
This guy has already played an old vampire, so it wouldn't be much of a stretch for this awesome actor.
Fifth recast: Rachel Mccadams as Mia Rinaldi
Well, we already know that this girl can be mean, having played in the movie mean girls as Regina George.
Sixth recast: Sarah Hyland as Natalie Dashkov
In my opinion, this was already perfect casting. No change necessary. Only putting on the list because she's kind of an important character.
That's all for my fan casting! Hope you enjoyed!