I'd consider a HAC drake, if you're taking 3, honestly, for solid AA, and if doing that probably switsh one of the Forgefiends to EPC rather than HAC. Your choice, of course, but otherwise: rather like some Dark Mechanicus lists I've idly considered myself, though I've never written them out.
What sphinx of plascrete and adamantium bashed open their skulls and ate up their brains and imagination? Imperator! Imperator!