You know how wasps are paraistic and lay their eggs inside other creatures. They hatch and eat all the non vital organs to keep the host alive until they are ready to emerge from the body, sometimes they survive that as well and guard the wasp larvae. I think it would be cool if chaos geneseed was engineered/mutated to do the same. Plant it inside a victim and it spread and grows like a cancer to make more of itself. Then they emerge from the body to be harvested and put inside CSM candidates.
Just something creepy and weird but has roots in the natural world so its not to 'out there' you know?