Circumstance boni are the DM's most important tool. "It's raining, +2 circumstance modifier to X" is essential.
And I suggest making shield give a deflection bonus. Simply because, well, shields deflect things. And keep things from touching you. So they should apply to touch attacks.
And why do you need specific profane/holy bonuses? You can only have one of them at a time anyway. You can just word it as "this spell gives a +2 divine bonus to AC to all good creatures" or some such.