this thread actually has made me want to try this build out. i'd do resto robes, whichever are level appropriate, along with the matching hood. steel, and then steel plate on hands and feet. i'd use a silver sword throughout the game (while leaving the difficulty at adept so it doesn't get annoyingly weak) while casting spells like turn undead and healing in the off hand. cast flesh spells before combat, while leveling alteration to 75 to get paralyze.
if a silver sword becomes unusable i might consider getting dawnbreaker.
i would definitely neglect block. just because the amulet fortifies it doesn't mean it's something a vigilant would use. never seen one with a shield.
oh and as to the questions about destruction, they do use it, often. i think i've seen them cast spells more than having a mace equipped.