my thoughts on the big nasty stuff is it could be used in two ways
a shock and awe beast for occasional use outside the fort or in a particular encounter (less is more, believe me)
and mainly a choas camp thing for rituals/blessings/etc (our toys

)
i run events with these pieces and they should be used only to enhance a situation never to dominate it. that just ends on a sour note. but as an enhancment to a situation would be very memorable.
what i will do is as my bestiary fills i will put pictures of the kits i have and nearer events the horde can decide if they want any of them to come along. i intend to make at least one of the main troop type deamons over this winter, so far we have the plaguebearers x3 (just the heasd to finish) bloodletters x2 ( again need to finish head pieces and hands, plus the hellblades) next on the list is a pink horror (just because from a maker point of view they are awesome visually) i am unsure of my desire to do a deamonette yet however

i have the claws for one done