Here's my revision of Akamai Nuva. I'll start out by saying I was very impressed with the original design. My design is only slightly different from the original, it just need a few tweaks in my opinion.
I don't have all the pieces of Onua Nuva or Tahu Nuva so I had to use pieces of a slightly different color. Which is why the Kanohi Hau Nuva is Black. (For some reason, the Hau Nuva always reminded me Darth Vader's helmet, so when I look at this black Hau Nuva I think "Darth Tahu".)
I've added a gear function to his hips and I've altered his weapon. I elongated his feet which give him better support. I feel the elongated feet are very reminiscent of how some of the Toa Nuva's feet appear longer when they use their dual-function weapons on their feet.
Here's a better looks at his weapons.
Building instructions are available on BrickShelf.