My first thought is, re-read glamour. Seriously. I used to think it was awful too, but then I read it more carefully and voila. Case in point, that damn Thomas knack. You simply can't ever bring a mage anywhere near them or they'll know who it is, right? Well, no.
First off, the players will play it off like it always works. And that simply isn't true. If you read
Apprentice Degree: The Blessing of Renown (PG p. 201) it clearly says that for any knack to work you have to spend a Drama Die.
Ok, so they have to expend 1 DD to get it started, but then they're safe, right? Well again, no. Take a look at all the other Apprentice Glamour knacks, some last as little as a single roll, and only one (Jack) lasts more than a scene. But if you look closer, the effect seems to dictate how long it lasts (get an extra something mundane until the next morning vs. add dice to a roll, once) So, why would Thomas last any more? My estimate would be a Scene. So, scene ends, Thomas ends and that means your player will need to remember to re-activate it. And that's the key of course, they need to remember.
But once they've got it up and paid for, they know all about your sneaky mages, right? Again, no. Take a look at the exact wording of Thomas...
Player's Guide, p. 203) wrote:Whenever someone (or something) that possesses sorcery comes with thirty feet of you, your left thumb begins to tingle. It continues to tingle until he or she moves out of range. When someone uses sorcery directly on you, you immediately detect what’s being done, and if you spend a Drama Die you may resist that magic.
So actually they only know there is a mage SOMEWHERE, not who it is, what kind of magic they have, etc. AND if you look at that sentence a bit closer, you'll notice that the definition of what a mage, or more specifically what triggers the thumb is also of contention. Take, for example a Sidhe Weapon, a Montaigne Puzzle Sword, or Dracheneisen. All of those have magic like abilities and there's nothing that precludes you from using those to answer your pesky Glamour Mage's question.
Now I'm not advocating you do this straight away, but if they're ruining someone else's fun (like say yours, which is important) turn their powers against them.
I'm certain that the other knacks have similar loopholes built into them.
But I agree with LG, if you have a problem with running them, ban 'em. It's your game after all.
Oh yea, one more thing, the GMG deals with the problems of having Mages in your game, (pp. 189-191)
"At times one remains faithful to a cause only because its opponents do not cease to be insipid."
Friedrich Nietzsche