Love the idea, add in some dungeon delving to obtain your holy artifacts, six unique weapons (three one-handed and three two-handed) each enchanted to do extra damage to an enemy type, a clothing set for Mage characters, two rings (one to replace the shield for those with the two-handed weapon set, the other for the Mage that could increase Mage armor effectiveness by a percentage), and a few new spells including four summon spells (as I would see nothing wrong with conjure familiar being cast by a Vigilant of Stendarr). Another suggestion is artifact reaqusition quests. If you were to run afowl of the Vigilant, then your artifacts would be removed. To regain admittance to the faction you must reaquire the artifacts. Come to think of it the scope and scale of all this, coupled with the delayed launch of the CK, makes me believe Bethesda already has plans for a quest line involving the Vigilant of Stendarr.