It would probably be better and cheaper for the project to recast (assuming there will even be an English dub, that is). At this point I’m not sure I really care. Maybe keeping the original cast would help fans that don’t like anime to connect with the project, but personally I can’t see myself taking any enjoyment from it regardless of who is in it.If it is an anime I hope they recast basically all of the voices. I like the English VA for Ren so I'd welcome them bringing him back, but for the most part I would prefer new, fresh, professional voice actors to give their takes on the characters. At the very least please recast Ryo
It is an anime though so they might only do subs for the English version to appease the nerds, which I would support.