The thought of Merriman in a Pats uniform makes me nauseous.
When you posted this I agreed with you. Now I'm not so sure. Here's what's changed for me:
1. The odds are against us being a "Final 4" team this year, i.e., against us making it to the AFCCG. If we don't make it, then even if we are a "Second 4" team we have some flexibility under the CBA rules for an uncapped year to sign external FAs without having to lose FAs of our own.
2. There is some clear benefit to adding a veteran DE/OLB pass rusher. Other than Julius Peppers, Merriman is probably the best one out there.
3. Merriman has improved over the course of the season, and seems to be coming back somewhat from his knee injury. He gives a lot of effort, and has gotten a lot more QB pressure than his sack total (4) would suggest. He has a great motor. His low sack total and knee injury should keep his cost down.
I wouldn't be averse to taking a flyer on Merriman if the price was reasonable. He's got an attitude, to be sure, but BB can usually manage that. Right now I'd take his attitude (and pass rush) over that of Adalius Thomas.
Signing a FA pass rusher would take pressure over having to hit early in the draft, and take pressure off a rookie, who could come in and develop more slowly (and also have a role model to learn from). If we got someone like Merriman we could draft one rookie pass rusher in the 2nd round - someone with a high upside like Greg Hardy (if he slips), Jason Pierre-Paul, Greg Romeus, Everson Griffen, Jeremy Beal or even Austen Lane. They could be brought along more slowly. We could then use our first draft pick to take BVA, possibly trading up for an impact player like Rolando McClain, Joe Haden or Cameron Heyward. If we end up in the 20-21 range (as opposed to 28-32) then trading up for one of those guys is much more reasonable.
I know, the thought of Merriman is a bit hard to take. But I think it actually makes sense right now. The only FA alternatives are Julius Peppers (30 and will cost a fortune, with no OLB experience) and Ray Edwards (whose sack numbers benefit from Jared Allen getting double teamed).