I mean, I would recast pretty much the whole cast if it was up to me so I could stick to book canon personality-wise, but to pick just one I’ll say that I’d have liked to see Christopher Plummer try to play Dumbledore before his death.

I really like the cast and I'm not sure I would recast anyone. Actually, there was some recasting done that I don't think was necessary, like Tom of the Leaky Cauldron and the Fat Lady. Their replacements were funny, and I like Dawn French, but I prefer their original portrayals.

None. The cast are perfect