The problem with One Piece isn’t so much the cast or the crew, but the fundamental concept. Cowboy Bebop actually does lend itself fairly well to live action, since it’s a short self-contained story that’s fairly grounded, and the gritty sci-fi setting is something that’s been done before plenty of times. With One Piece though, adapting the main story is a futile concept, and the setting and powers are inherently cartoonish. The ONLY way to do live-action One Piece though is to ignore the main plot and just do a side story ambiguously set some time during their voyage. Sort of like the questionably canon One Piece movies, except it just happens to be in live action. If they do this, there’s certainly a chance that the end product will be watchable - possibly even good.