Some interesting points.  I'll add another one: it's quite possible for the players to be proactive when their characters are reactive; I have had quite a bit of fun playing a wizard who really just wanted to be left alone to study... and was loaded up with aspects that ensured that wasn't going to happen.  I was fairly proactive about finding ways to get those aspects compelled, but the character was essentially reactive - and, given a few weeks (or months or years) of downtime, he'd happily spend it working on magical research.

Sounds about right. In practice it just means that if a Wizard wants to shield he can do so early in the exchange, rather than wait for his turn. Not sure how I feel about that; other characters don't get to rework Initiative like that, but it is limited.

Actually, they do - there are several mortal stunts that allow you to do something now in exchange for losing your next turn; that's why I proposed being able to do that as requiring a reactive shield stunt (or a relevant aspect and a fate point to invoke for effect).

The question to ask now is whether ambushes would lower your skill to 0 and how that effects rote spells.

If you're truly unaware of the attack, you can't put up a reactive shield.  Period.  Well, unless you've got something like, say, an aspect relating to precognition and a fate point to burn.  This is where stuff like Harry's duster shines - in IC terms, it's an always-on defense, which justifies using one of its OOC-limited charges against an unanticipated attack.

Uhm... Yes it is?  The "same catch" in this case being, for the above example, "ice/cold effects of weapon rating 3 or more".  There's certainly no rule against adding extra limitations that you don't get a rebate for (and in fact that's often a good thing that gives you more chances to net fate points from compels on your aspects), so I really don't see why you'd argue against this based on "rules-as-written".

I haven't had a chance to look at it yet, but it seemed the sort of thing people on this forum might want their attention called to: http://www.evilhat.com/home/the-fifth-day-of-halloween-week-and-treats/

There's actually one more possibly-important question here: When this battle came up, did you, as the GM, hold up a pile of fate points and say "By the way, since you're Under Investigation by the Wardens, it'd be a really bad plan to kill using magic here..."

If so, and if they took those fate points and then went gung-ho anyway, then go right ahead and complicate their lives.  If they bought off the compel, then maybe the Warden investigating knows about the local vampires and Renfields, or maybe there's some other power in the area that decides to claim responsibility for destruction of tools of the vampires...

Hm.  Some interesting thoughts in this thread.  Here's how I'd generally address some of these:

There is no "roll" in moving between zones that lack terrain features between them that your character sheet can't automatically overcome (things with legs can walk across a parking lot, things with wings can fly over fences, aquatic creatures can cross a river).

This one's false.  You get one free shift of movement as a supplemental action; if that's not enough to change zones, then you need to make an athletics action to move.*  And for this, it doesn't matter if the zone border is a 'natural' one (say, from an inconveniently placed shrubbery) or resulting from a block (say, from an earth wizard raising up a wall in the middle of the parking lot) - either of these will prevent movement.

* Footnote: some exception may be made for creatures with extremely high strengths; there are rules for what you can break (I think it's something like might -8 or somesuch?) without requiring an action.  Of course, this requires the block be one that can be just punched through with raw strength; a black court vampire might not slow down for a locked interior door (just breaking through it), but a threshold or act of Faith would not be so vulnerable.

Now, say that wizard brought up a wall - and it's a +6 block, versus your athletics skill of one.  You can't directly overcome the block; even with a +4 on the dice, you're out of luck.  What you *can* do here is spend an action to try to remove the block, breaking it down with might or magic or maybe just scrounging up a fire hose to short out the wizard's abilities.  That's a basic opposed roll - and if you take the -1 penalty for a supplemental action, then (assuming your roll succeeds), you'd be able to break the block and move one zone after.

For blocking things that aren't measured in shifts - such as most shapeshifting - you'll want a compel.  Succeed at a maneuver, use your free tag for effect to trigger a compel.  In some cases, this'll be a freebie; put up a circle around a wizard who casts shapeshifting spells, and (unless he saw what you were doing and prepared a counter-maneuver to draw in power or something), that's that.  In other cases, it'll just fail - put up a regular circle to try and lock down a loup-garou, and you're just out of luck.  But hey, that's compels for you.

Now, there are some cases where you can clearly block shapeshifting with an actual block action.  For example, the Human Guise power mentions discipline checks to maintain a human appearance; you could use intimidate skill to incite such anger that your opponent can't shift back, for just one example.

I'd definitely look into Greater Glamours & Breath Weapon.

Also note that a Sponsored Magic doesn't necessarily have to have a 'real' sponsor; examples to the contrary being Kemmlerian Necromancy, as well as Ley-Line sponsored magic.  Of course, if you're going to actually take any sponsor debt, you need to work out with your GM how that's going to come back to haunt you...