Stealer hybrids aren't exactly known for their looks .. not til they get to 3rd or 4th generation hybrids at least :)
And there are rules for playing them in 40k coming in White Dwarf.
Cool! Genestealers are an interesting concept.
Going to share it?
Not much to it, admittedly... My idea is that this Cult is headed by a Wych that got betrayed and nearly killed by her old group. So, she tries to start a Cult of her own, gathering rejects, victims etc. from other groups. The Cult is small, but the plucky Succubus is determined on making alliances - so, she entered into a mysterious agreement with a leader of a Mandrake clan. What the agreement entails, she doesn't say, but she seems to have been... shaken and changed by her negotiations with the Mandrakes.
She also tries to secure some Haemonculi monstrosities for herself, but she's careful, as she hates and fears the Haemonculi themselves. Still, she wants to have one of the Pain Engines for her Cult...
IIRC the Exorcist is built of the rhino chassis, and it's also an old kit. When it was created, GW were only using plastic for the massive run stuff, like the rhino and all its variants. Over time they've shifted more to more plastic kits, and resin over metal, probably for manufacturing cost reasons. An engineer friend of mine who knows about this sort of stuff said the start up costs for plastic are about 10 times that of metal (or were back when we discussed this), even if the ongoing costs are cheaper. Sisters wouldn't have the sale volumes to to make all plastic financially viable.
Anyway, the Exorcist has no assembly instructions, dammit! I need to google for it...