honestly not trying to start anything here, because I quite like the casting of PE too (on the basis that he's actually the right age rather than 30 years too old, as per the movies, and AR was so iconic that anyone similar would struggle to do anything with the role that didn't come across like a weak cos-play, so casting someone who looks completely different allows for a new interpretation which will be more interesting, also having a black actor works with the 'outsider in both worlds' part of Snape's character).
but what's your interpretation of 'as faithful to the book as they promise.' i.e. what elements can be changed and what are non-negotiable?
Because if you are happy with the PE casting (and, again, I have no issue with it), surely you accept that that already is quite a huge departure from the books in terms of Snape's physical appearance, which is repeatedly described as pale, greasy hair, etc.