Overtkill, use a chaos space marine obliterator body and just green stuff the rest. Spawn would be a problem the cape would pe solid to sculpt. As for violator I think the best bet would be to thin out the extremitys (arms,legs) and use a bloodthirster head maybe.
You have just opened up a whole new world of modeling opportunities for me. Thanks for the inspiration .
Independently targeting particle beam phalanx. Vwap! Fry half a city with this puppy.