So heres my ideas so far!
Dont forget I wont convert this is for a bit of fun! But I will re-write the codex with different names etc for the units I will use (None of the rules or points costs will change, basically cutting half the units out and limiting my options!)
Codex- Chaos Space Marines-
Everything has mark or Nurgle,
HQs-
Warpsmith- I am sure you can work out why!
Deamon Price- Haven't decided how yet, but a giant robot with wings?
Elites-
None I think
Troops-
Cultists- Basically the minons of the Dark Mechanicus
Fast-
Helldrake- Flying robot dragon!! enough said!
Heavy-
Forgefiend and a Maulerfiend! Giant robot monster things :D
Defiler- going to change the design of this a bit tho, to make a crawling spider looking thing!