May I present the most compelling evidence to NOT chnage your voice actors. At least, not for a HD re-release...
My favourite game... butchered forever!
They kept the same voice actor for April Ryan in both
The Longest Journey and
Dreamfall and I didn't even notice! I think it's because she sounded significantly more grown up, which is part of her character in
Dreamfall, but I definitely felt better about it once I knew. Strange, must be a psychological thing.
Lara Croft seems to have had the most voice actors for any video game character (5 over the course of 10 games) and yet no one ever cares about that. So long as she sounds female, posh and British it doesn't seem to matter.