Re: One Piece Mega Convo (Spoilers!)
Chopper's design is because of the seiyuu. Being a monster was the original idea for Chopper, but when Oda heard the actor voice he changed his mind and did Chopper as cute pet.
Not quite. Remember, Oda DID draw Chopper as a monster originally. But that was partly because he's sometimes awkward at drawing new characters (Usopp looked horrible during the Kuro arc. Simply horrible). Chopper was drawn quite badly on Drum Island, but over the course of Alabasta, Oda got used to it. The way he drew Chopper around late Alabasta/Early Skypiea was probably the best way, he looked like a chibi-reindeer, which is what he is in Brain Point. But over time, he shifted from looking like a chibi-reindeer to a furry child. It's a problem, and it's Toei's fault. They got Ikue Otani (voice of Pikachu) to do Chopper, and marketed him as the cute animal mascot, which is exactly what Oda was trying to avoid doing with Chopper. But once Toei did it, he had to shift Chopper's character design, and to a point, his characterization. I think that Chopper was always supposed to act like an admiring younger brother, but sometimes Oda has him on the line between "admiring younger brother" and "hero worshipping fan". Again, blame Toei.
But that's not the only example. Oda always wanted Mayumi Tanaka to voice Luffy, he thought she'd be perfect for him. That's why he was ecstatic when she got the role. It just worked out that way, it wasn't on his request. However, he DID draw Franky with Kazuki Yao's voice in mind. Franky was in a sense designed for that voice. I don't think Bon Kurei was, and I don't think that he cared that that voice had been used before, but Franky's voice actor was sort of determined from the beginning.
That said, Oda drafted the entire story before the anime even started. While he may have created certain characters with certain voice actors in mind, there wasn't even an anime to take into account when he came up with the story, and so the odds that the anime would affect something as crucial as which characters join the crew are quite low. If Oda intended Bon Kurei to join, then he will, and whatever decisions Toei has made won't matter. And if he didn't intend Bon Kurei to join, then it's all academic anyway.
If Bon Kurei does join, then something will have to be worked out, perhaps with another voice actor taking Bon Kurei. Or Yao just doing both of them. I don't how often voice actors take two roles at once in Japan (Masako Nozawa was at one point doing Goku, Gohan, and Goten, but I think that's pretty rare), but there is a precedent, and it can be done. FUNimation's Dragonball Z dub was done with about 10 voice actors, many of whom spent hours in a booth talking to themselves (Vegeta and Nappa, Goku and King Kai, etc.)