My general rule of thumb has always been that player that everyone considers the 'must have' the 'beast' the 'guy we desperately need' never turns out to be that guy.
Personally I think the most overrated players in the NFL are guys who only rush the passer and dont even pretend to play the run (Freeney is the classic example). I think this is partly because fans love sacks, partly because the media does and at least equally because sacks are about the only stat that a defensive player can point to and have it affect his paycheck, so it gets overhyped all around.
I want my defensive player to play 1000 defensive plays effectively. 400 or so of those are running plays, unless I cant stop the run and then 600 are. I want my defensive players, especially the ones I shell out the most money for to be effective, and not a liability on 1000 plays rather than have them give me 15 exciting ones. This is why comparison of say Richard Seymour and Dwight Freeney aqre ridiculous. They arent even in the same area code. Seymour plays every down, and does everything a DE is supposed to do very well. Freeney rushes the QB 1000 times, gets run past he is spinning out of position on a run play and gets some sacks. He is a liability on 20 plays for every sack he gets.
For all of these reasons, I am against Peppers coming here. He surely isnt as one-dimensional as Freeney, but he is first and foremost a guy who only cares about sack numbers. Thats not our style. He is not awful vs the run as a 43 DE, but far from good, and that translates to trouble if converting him the a 34 OLB.
Trade for Peppers, get a sack a game, make everyone think it was a great move because there is a number to judge him on, and you end up with a guy who helped you on 15 plays (whoever else was in his spot probably would have done half of that anyway) and weakens you on 400+.
BB has never had a 'small, speedy, passrush specialist' not because they are expensive but because they just dont fit his philosophy. What you lose with that type of player is more important to BB than what you gain.
Go find one who can also play the run like a Mike Vrabel, and BB will beat down doors to get him, but I haven't seen that guy out there to get.