I don't really see how you could adapt One Piece without going full high budget CGI extravganza which I don't think is doable on TV. It's not like i don't like the idea of it, One Piece has a fun setting and fun characters and fun story arcs but unless you embrace the cartoonyness of it all and adapt it as best as you can you're just gonna end up with some bland story about pirates with superpowers.