I see stunts and the sheer amount they can get to be the way Pure Mortals can compete with Wizards, White Court Vamps, Knights Of The Cross, and Wereforms.
I see nothing wrong with assigning them as many of them as the player wants, and further more would rather quit a game then have a GM who would limit what I can and cannot do with MY character so long as it does not break game balance.
And as for the Deceit stunt, if that is what I as a player wants and its plausible and by the mechanics legal then I expect the GM to keep his mouth shut.
I totally agree about the stunts; as an ST I would never limit the amount someone could take. My group is very... optimized? efficient? and so they really want to look at, "is this stunt a worthwhile investment for me", almost a bit over "does this better define my character?" And the advice that luminos gave is fairly solid, and how my group thinks, but it's not for everyone. However, a bunch of fate points is a significant advantage for a mortal. As an ST, I would feel obligated to point that out, and make sure to ask the player (as i did you) how (s)he felt about taking so many stunts versus leaving fate points open. I didn't mean to imply that I thought they should be limited.
As for the deceit stunt, it's not really legal/illegal by mechanics, so it's completely fair for the GM to question it. In fact, the mechanics dictate that there be a bit of back and forth between the players and the GM to settle on such a thing. Reading over the example on 147YS, where the player wants to transplant dodge to guns, the GM offers two conditions: the first is that it only works when the character has a gun close at hand, the other is that it only applies to ranged attacks. So by the book, transplanting dodge deserves a limiting condition.
My real concern with it is that it allows deceit to pull double duty for defense, defending both physical and social, and that it appears without a limiting condition. Now, the limiting condition need not be very restrictive (as above, requiring a character who has invested 5 skill ranks in guns to have the gun on-hand while dodging... not really limited). But, as it stands, your character could be giving a speech, and someone shoots at him, and he defends with... deceit? It conceptually makes little sense there. I get what you are saying about feinting (and I read where someone else suggested it as more appropriate than, say, presence)... but I still don't really see it. If I was the GM, i would probably just ask for a restriction that you must either be moving or have moved in the last turn, or for you to come up with some equivalent justification. Hell, if you'd described your character as always moving, or constantly fidgeting, maybe with something like that as an aspect, I wouldn't ask for any more justification.
I'm not trying to argue or persuade you, just trying to offer an opinion on why that may not be as rules-solid as it first seem. It certainly doesn't break the game, but it is perhaps more overpowered than -1 stunts.