Ok, so there are two power concepts that I run across a fair amount in my fantasy reading, but that I have yet to figure out a good way of incorporating into the game.

1: Supernatural Luck: You know the concept: A character for whom everything just goes right. He can walk through the middle of a gunfight, and all the bullets just happen to miss him. He goes out for a walk and happens to trip over a briefcase full of money or the crucial piece of evidence to solve the mystery. His car never breaks down, he never gets caught in the rain, and even the birds always miss him.

Now, obviously this would be easy to implement by just giving a character loads of Fate points, but that feels a little too easy. I want there to be a catch to this power, some way in which relying on your power to tip the scales of Fate can come back to bite you. The best idea I've had so far is that taking this power also gives you an Aspect along the lines of "dependent on luck" or "weird luck", and that you cannot buy off Compels related to that aspect.

2: Inhuman Vulnerability: Taking things one step beyond the Catch, this is the case where not only do your powers offer no protection against a threat, but you are far more vulnerable than a human would be. For example, a lot of werewolf stories feature the idea that a werewolf is so vulnerable to silver that the slightest scratch from a silvered blade is death, and even touching it can burn. At the lower end, I imagine you could implement this with a "power" that gives certain attacks extra shifts of strength against you. For the higher end, I'm considering a rule that says that you can't take Consequences to buy off damage from whatever you're vulnerable to. You can still take stress hits (fluff-wise, because stress generally represents strain and near-misses rather than actual harm, crunch-wise because that keeps it from being quite so crazy brutal), but if someone actually lands a hit, they're taking you out.

One point that might be relevant regarding the First Law. It's a fairly well-known fact that humans have an instinctive block against killing other humans. This used to be a huge problem for armies, as a lot of soldiers would "freeze" when they needed to kill under extreme stress. So what the army started doing was taking people and retraining their instincts, putting them under extreme stress and making them "kill" dummies and practice targets again and again and again, until their reaction under stress was not "mercy!" but "kill!". I've begun to suspect that breaking the First Law does much the same thing, except much faster.

As the analogy above suggests, I don't believe that this necessarily makes the wizard evil (and I don't think the White Council does either, as suggested by the Doom of Damocles), but it does make him dangerous. Possibly dangerous heroic (like any good soldier), but still dangerous.

Let's see. If I remember my Lore correctly, Hecate is the goddess of magic, so I'd have her magic give a +1 complexity on any form of Thaumaturgy. Hades, I'd probably use the same bonuses as Kemmlerian Necromancy.

I think this is more my problem with the system then - the scope of which players have control of the story is a bit much for my tastes. I like to keep players declarations within reason - 1 fate point is enough to make small declarations (an object that makes sense being in a location is explicitly there, someone forgot to lock a door, etc.) not huge changes such as might rule out any obstacles I may have planned out for the PCs, such as the item no longer being in the possession of the bad guy, or X character knowing where and what the PCs are after.

Well, that's easy to handle. There's no rule that you have to accept a declaration, even a FP one. In fact, the rules on the subject say

This gives you the ability
to create things in a story that would usually be
under the GM’s purview. Typically, these things
can’t be used to drastically change the plot or
win a scene.Declaring “Doctor Keiser drops dead of
a heart attack” is not only likely to be rejected
by the GM, it wouldn’t even be that much fun
to begin with. Declarations are better suited
to creating convenient coincidences. Does your
character need a lighter (but doesn’t smoke)?
Spend a fate point and you’ve got one! Is there
an interesting scene happening over there that
your character might miss? Spend a fate point to
declare you arrive at a dramatically appropriate
moment!
Your GM has veto power over this use, but
it has one dirty little secret. If you use it to do
something to make the game cooler for everyone,
the GM will usually grant far more leeway than
she will for something boring or, worse, selfish.
As a general rule, you’ll get a lot more lenience
from the GM if you make a declaration that is in
keeping with one or more of your aspects. For
example, the GM will usually balk at letting a
character spend a fate point to have a weapon
after he’s been searched for them. However, if
you can point out that you’re Always Armed
or describe how your Distracting Beauty
kept the guard’s attention on inappropriate
areas, the GM is more likely to give you some
leeway. (This is much like invoking an aspect,
but without a die roll.)

A couple of new things I thought of

First, a new stunt for Wizards: Exclusive Power (needs a better name)(Discipline): You have gained a measure of control over zone-effect spells. When casting a spell that targets everything in one or more zones, you may exclude a number of targets equal to half your Discipline (rounded up) from its effects.

Second, a cluster of powers: Spell Resistance (-2), Improved Spell Resistance (-4), and Greater Spell Resistance (-6). All spells cast on you are reduced in power by 2, 4, or 6 shifts depending on which level you purchased. If this would reduce a spell's power to 0 shifts, it has no effect whatsoever. You may choose to attach a Catch (specifying a certain kind of magic that you are not immune to, or specific circumstance under which your Resistance is negated), but it is not mandatory.

I think that's a logically sound argument but I disagree with it just the same, on the basis that The White Council doesn't really care about things outside magic, by and large. If Harry Dresden had killed a mortal with an icepick for no discernable reason rather than kill Justin DuMorne with magic in self defense, he wouldn't have found himself under the Doom of Damocles.

I think non-magical morality seems to be something they're fairly disinterested in, as unpleasant as the implications of that are sometimes.

It's not just non-magical morality, but morality period. As Luccio pointed out, the Laws Of Magic aren't primarily about right and wrong, but about control, binding wizards and limiting their danger. The Council stands neutral on matters of right and wrong because it's the only way they know to prevent civil war.

Speaking of ancient Wizards...I wonder how the White Council acts when it comes to issues of race and sexuality.

Slavery was legal in America until 1863. That's only 150 years ago, there are people in the White Council old enough to have owned (legal) slaves in their younger years.

I would hope that the international nature of the Council would help with that, but...I'd expect a lot of senior Wizards to be old-fashioned in the worst sense of the term.

Since magical talent is not affected by gender or ethnicity, I'd suspect the Council's "powerism" trumps their racism or sexism.