Hailstorm

Loki would be cooler. Luffy's crew is made up of wild and interesting humans and non-humans. Loki would fit far better in that category. I mean, Vikings are classicly known as the sailors of seas and ocean travelers. Loki suits far better in that and I hope he is the next oddball to join the crew. I think it would be boring if Bonny who is kinda a copy to Luffy would be added to the main crew. The Grand fleet seems more her style since she also has no reason to leave her crew. Viv is also a good choice. Loki is best and for those saying about his size, where's your imagination, you don't think it's possible he can alter his size.