This issue is completel overblown. I just can't see what the advantage really is here.
You have to have a guy watch the signals in the first half, break them down in 15 minutes and be ready for the second half. In the 15 seconds or so to get the play in, the coach has to recognize the signal, and call the appropriate play, get the information the sideline and have that coach get the play to Brady. That's not going to be easy to do. I'm guessing the Jets have more than 2 signals that they use.
I don't see this as being any different than signing players and /or coaches from other teams and then asking them for inside information. If we signed a player from the Eagles defense, I would hope we might ask him what hand signals means quarters or zone or man-to-man.
Furthermore, given Mangini knew the Pats did it, he is a complete moron for not changing up his signals and using it to his advantage. He should have changed the 2 deep zone signal to corner blitz for the second half and knocked Brady on his ***.
There is no way that this effects the outcome of a game more than a player on steroids like Shawne Merriman. Or even the Broncos winning SuperBowls and cirumventing the salary cap. Or dare I say it, even the Cowboys in the mid nineties who were obviously doing something to mask drug use.
Now - they were warned about this in the past and it is against league rules. A fine and the loss of their 1st round pick is probably enough to deter others from doing the same.