For me, it's almost a tie between Lewa and Kopaka. But in the end, I'd say Lewa for sure. His mask is awesome. I also like Pohatu a lot too. The others, not so much.
I'll be checking this often, definitely! Do those wires that keep Niaka awake have anything to do with the wire (or cord) Rathoa found in CoT. Also, I have this nagging feeling the Kuambu and Bhukasa's species are related somehow.