The SBG is a nice start if you're paying someone to make a fortress, but, honestly, your best bet would be to pop stone and iron walls with Wall of Stone/Iron, Shrink Object the mass of materials before Fabricating them into the desired structure. Stone Shape would more than likely be used to secure the underground with Passwalls here and there for secret exits and the like.

As for anti-scrying, a Mindblank a day will keep the trouble away.