I saw a light grey part of Kaxium on the Agori that looks like it could attach a life counter... could someone get me a shot of the Back of Kaxium, please?
Also, I agree on Cendox.
Couldn't find a pic from the back on B6's flickr page. But I got a pretty could side view for the side car, and the agori uses a Toa Newva/Av-Matoran connector piece to sit him in the Kaxium. That may or may not have been what you saw.
As to modifying sets; I don't. Except for one little tweak to Kardas. Oh, and I changed Ehlek's borken lime pieces with bleh pieces. It didn't look to bad, but it wasn't the same.
At BZP, there is however a good modification to Gresh in the Tarduk review. He has Inika Shoulder armour in lime(presumably from Rockoh), piraka leg armour, and pieces fo attach to the other end of his hand to create staffs instead of armblades. Pretty cool, and he got Tarduk's helmet.
my armmor suggestion fixes that.

That only seems to make them shorter, because in reality you are only changing the thinkness of the thighs. I wish he had bigger thighs too. I never liked the bitil legs... He should have been given lower tahu legs and upper piraka legs.
And, sadly, Telluris may have Keetorange... Too bad. Perditus and Sahmad look to have the same helmet ><
Both Kaxium riders have the same helmet too ><
Kiina's helmet colour does not go well with the rest of her body. Why could they have not gone with a colour that matched?