Can't wait to see this thing done. I think you should go with copper for the rims :) Not that i don't like your weathered white , which i do . I just think It would look more natural with the copper.
Copper Rims.Bronze/Brass/Copper with verdigris screams Dark Age of Technology mechanica.
White rims will looks wierd when you already have copper rims on teh chainsword and head, but even if you didnt, it would still look strange I think with so much else going on in the model ie bright orange, black, lots of silver, yellow checks, etc.