the problem is you can't really have James as a POC if Harry is white
Same with Sirius - having a black Sirius Black is a bit too on the nose and again would have a knock on effect on the casting for regulus, bellatrix, narcissa, andromeda, tonks and even draco, as they are all supposed to be related.
Lupin could be a possibility as it would work well with his 'othering' but would it be a bit too much?
The only issue with Pettigrew would be if there were too many of the death eaters of non-white origin.
It also seems a bit off to not cast people who could be the best fit for large roles from series 3 onwards solely due to who you'd have to cast as their younger versions for a 30 second scene in series 5 - which you might not ever get to if it gets cancelled before then. They might be better off just cutting that scene, tbh.
I don't care strongly either way. My initial thought was that anyone (like Adam Driver for example who was the fancast) looking like a 'traditional' Snape would struggle to separate their performance from Alan Rickman's (someone on another thread put it brilliantly as a 'Temu Alan Rickman') so having the character look completely different at least separates that and gives PE a chance for his performance to be assessed on his own merits. OTOH the whole sell for this series was it was supposed to be far more faithful to the books, and drastically changing characters' appearances doesn't seem to be living up to that.
I just hope they don't cast just to appeal to a 'woke' audience, because the people who feel strongest about that are going to be boycotting it due to their hate for JKR anyway.
I did laugh when I saw a post from a TRA on reddit or somewhere saying smugly how the series was bound to fail due to so many people boycotting it after the SC ruling to stick it to JKR - yeah that didn't work with Hogwarts, a Legacy, or any of the HP books which are still, after more than 20 years on the top of the best sellers charts, or the CS series, or the theme parks (universal have literally opened another HP one this month), or the Watford studio tour....
They don't seem to understand that, to counter the fairly small amount of people who feel strongly enough about JKR to boycott anything related to her, there are others who want to show their support of her so will watch/read/buy her stuff even if they aren't interested....and that both of these groups are dwarfed by the majority of people who don't really care either way, and if they like something they'll watch/read/buy/visit it, and if they don't they won't.