Especially considering Snape in the books is described as having sallow skin and long, greasy black hair (and a hook nose, though that part is less important given policing a nose type on the actor is a little weird). I'm sure Paapa is a great actor, but Snape constantly has his appearance (especially his hair) described throughout the book series, and it would be nice if they retained it. If they want more racial diversity, Lavender Brown was a black girl when she was a background actor, and in the books, Cho Chang is Asian, Blaise Zabini is black, Lee Jordan is black, Kingsley Shacklebolt is black, Dean Thomas is black, and I'm pretty sure so is Angelina Johnson. Nationality-wise, Durmstrang students are Bulgarian, Beauxbatons students are French, and Seamus Finnigan is Irish. Furthermore, I believe it possible to add more Irish actors if they wanted, like perhaps Luna Lovegood being played by an Irish girl again like Evanna Lynch's portrayal of her.