Why does it have to be a "big-time" replacement? How about an "effective" replacement. Aaron Kampman was\is hardly 'big-time' but he gets the job done with hard work, film, and hustle. He isnt the biggest or the best, and....ok im rambling, Kampman rules. But you get the point. Get someone who can DO the job. Kampman(kampman types) isnt a one trick pony. He does an above average job on pass AND rush. He isnt a 'pass rusher' and he isnt a 'run stopper' and...ok im rambling again, Kampman rules.
YOU GET THE POINT! LOL!
In my opinion, KGB is effective. So a replacement who is merely "effective" would not be an upgrade. If Thompson could replace KGB with an equivalent player for cheap without taking a cap hit, that would be fine. I just don't think it would be as easy to find an upgrade, or even a cheap replacement, as many others here seem to think.
As for Kampman, he has always been effective, but this year he has really become something special. There are not a lot of players like Kampman floating around the league waiting to be signed to cheap contracts. That's why Thompson paid so much money to hang onto him.
And make no mistake: KGB works VERY hard out there.