Dudes, IW with IG allies would be awesome. get the cheapest HQ you can find. Get Penal Legion (use cultist models). Then get 1 battery of 3 Basilisks. Top it up with fortifications and AAA. And that supports your main contingent of IW marines with maybe 2 Vindis and a Defiler, lots of IW marines, maybe complement with a squad of chosen or possessed to take advantage of breaches in enemy defenses, a lord or DP HQ. If got points, then definitely the Helldrade because it's such an awesome model