Reposting here because I'd love to see it -
I think David will want an army of automated pilots to spread his creatures throughout the galaxy, thus it follows that he may capture some engineers, conduct mutations on them/insert technology in them, etc, etc, and implant them biomechanically to the juggernaut chairs, thus those particular engineers will be enslaved to serve David for that singular purpose of piloting the juggs to infect worlds; he'll make them one with the Jockey chairs, metamorphosed and elephantine.
