I can't see this being any worse of a reflection of the manga than the anime is, especially if Oda retains any kind of creative power and Adelstein's statement is legit. I've been thinking for a while that One Piece absolutely has the potential to be a kid friendly Game of Thrones. It has the massive world full of interesting characters without the sex and gore. Also, Game of Thrones is difficult to get into since it throws a shit-load of kingdoms at you right off the bat and branches off into even more locations and characters. One Piece is more user friendly and allows for a more gradual build with the audience learning about the world as Luffy does.
Obviously it requires major changes to be watchable, changes to things that kind of embody the spirit of One Piece. It needs to maintain a lighthearted tone, but it can't be quite as goofy as the manga is. Real people just don't act like manga characters and they REALLY don't act like One Piece characters. Luffy can still be dumb and care-free, Zoro can still be single-minded, Nami can still be money hungry but everything needs to be toned way down. Use some of the goofier character designs as inspiration for cool looking costuming without actually having Zeff wear a ten story chef's hat.
I'm also curious just how close to the story this series would go. Live action shows like this usually hinge on dramatic reveals or character deaths for climatic moments in a season. I know One Piece isn't completely devoid of that stuff, but the climax is usually Luffy punching someone. There could still be fights but they might have to come up with more "clever" ways of beating the bad guy, especially since they will likely tone down the magic powers. The flashbacks would be essential, but they might have to find more creative way of working them into the story rather than dumping the whole thing at once.
I'm interested what this will actually turn into.