Given that Acroflagellants were originally a SOB unit, it would be more surprising if they weren't in a SoB codex after having appeared in the GK one, particularly since they've gone to the effort to make them actually useful (and actually do what you tell them). Plastic...doubtful. In GK you can only have more than a few of them if you use a particular Special Character, and I doubt they'll be -that- much more common in SoB. Of course, buying a unit of up to 12 of them in blister packs is painful even so, so you may be right. The new rules for acro flagellants and death cult assassins add a lot more value to a SoB army than a GK army, so even if inquisitors are removed, both will be present in a SoB codex.