They said earlier already that they want a diverse cast because often it didn't receive such. If we take Death Note again as example, they basically americanized the whole story and made Light a whiny little bitch and he wasn't even asian. He wasn't even Light Yagami anymore, he was Light Turner. We don't want that shit. All we want is some diversity but keeping it close to original.
They try to follow what Oda provided in SBS from the questions "where would the Strawhats come from if they are from the real world?" and Oda said Luffy would be from Brazil for example. Doesn't mean that he has to be black. And Lewis Tan (who a lot of people hope that he plays Zoro) isn't japanese either but british-chinese. I do think they will try to follow Odas ideas and pick an international and diverse cast but also try to make it look natural.
I get it and I'm all for it, but Brazil is multiracial country with very diverse population, some of them are white, some of them are Asians (mostly Japanese), some of them are black, some of them are the native people, and some of them are racially mixt. So, which type of Brazil are they going to pick? If they go by the look then Luffy should be played by white guy but SJWs will come and say that white guy doesn't represent Brazil's population and if they pick some other race then the one piece fans will be mad that the MC doesn't look like Luffy, so what are they going to do? Well, they're going to go with the middle ground by picking a racially mixt guy for Luffy's role just like they did with Zoro.
It hasn't been confirmed that Lewis Tan is going to play Zoro but if it's him indeed, then I wouldn't be surprised cuz Netflix has the same problem with Zoro just like with Luffy. If they go by the look then Zoro looks like a white guy and Oda loves to represent Japanese as big muscular guys (look at Oden and other Samurais in Wano) and Zoro's facial features doesn't look like asian ether. Zoro is Japanese/asian and Sanji is France/white but they have the exact same facial features.
Finding an asian guy that is muscular and looks like white guy and on top that knows English is impossible, so if they pick a regular asian actor then he wouldn't look like Zoro whatsoever but if they pick a white guy then people would be mad since a white guy will play an asian character. Nextelfix chose a racially mixt guy "Lewis Tan" who looks more white than asian, in that case they have a white looking guy who has asian background and everyone happy. I'm pretty sure that they are going to do the same with Luffy to make everyone happy but I don't think that they will be able to find the right guy for Luffy.