What if scarab swarms were litterally just CAP? Or had an inbuilt effect like using turrets when boarding as boarding value (sounds kinda like tyranid spores). Hmm.. Other than copying the nid theme of little expendables floating about a ship I can't really see scarabs being used in BFG.
As an inbuilt effect I can see scarabs giving bonus's to boarding, ramming, turrets and possibly as part of the armour save (living metal save). This could be a refit... Hmm
Cheers,
RayB HA