Had this idea, not 100% sure it's a good one but figured I'd do a quick bounce off of people here. I think it has good flavor but may not be a good winning force:
format : rules used ----> representing
Primary detachment is Chaos Space Marine.
HQ
Typhus ------> Genestealer Patriarch
Troops
Cultists-Zombies ------> Purestrain Genestealers
Cultists -----------> um...cultists
Heavy
Havocs ---------> Hybrids with heavies/specials
Allies could be summoned Deamons (old cults could do that if they were joint Genestealer/Chaos) or Guard with a Primaris being a Magus and the Guard being brood brothers.
Thoughts? Other units to represent? Too soon for counts-as armies?