On paper, these teams appear to have personnel better suited for the 3-4 alignment. However, because I do not have an up-close-and-personal knowledge or relationship with those players, I do not know if the 3-4 would fit their skill sets rather than just their sizes and the lack of a true pass rush from the down linemen.
I must emphasize that in the 3-4, the down linemen are mostly occupiers rather than playmakers, so as long as they free up the linebackers, then they have *usually* succeeded at their job.
Each of these teams could then acquire Julius Peppers by trade. The Raiders could offer DE Derrick Burgess, while the Bengals could offer rookie DE Michael Johnson and a draft pick, while the Bills would probably have to offer a package of draft picks.
The Oakland Raiders
In the draft, they made some scratch their heads. I say let the players decide that on the field before making broad generalizations. Anyway, the Raiders selected DE Matt Shaughnessy, DE Stryker Sulak, and DE Slade Norris, all of whom have the size to play linebacker, especially in the 3-4.
On the defensive line, Gerard Warren and Terdell Sands have the right size to play the nose, and Jay Richardson and Tommy Kelly could play ends.
There is also the question of whether new Raiders defensive coordinator John Marshall is comfortable with the 3-4. From his bio on Raiders.com, he has spent most of his career working with linebackers, which would be conducive to the 3-4, but the bottom line is I'm not sure that Marshall is interested in the 3-4.
Conclusion: Al Davis is no stranger to the 3-4, so if he wants it, he'll get it.
The Cincinnati Bengals
The Bengals had an above-average defense in 2008, despite their record. However, they lacked a pass-rush force from starting defensive ends Robert Geathers and Antwan Odom, while the backups were virtually non-existent.
With Jonathan Fanene, Domata Peko, and Tank Johnson, they have a trio that has the size to play the 3-4. Meanwhile, Antwan Odom looks like he could transition to rush linebacker.
The Bengals selected ILB Rey Maualuga and DE Michael Johnson in the second and third round of the 2009 NFL Draft. Maualuga would fit well in the 3-4, but I'm not certain about Michael Johnson.
Conclusion: The 3-4 makes sense for their personnel, but their draft selection of Michael Johnson seems to conflict with the 3-4.
The Buffalo Bills
The Bills selected DE Aaron Maybin from Penn State in the 2009 NFL Draft, who has been projected as a linebacker in the 3-4. However, Maybin is similar in size to current Bills defensive end, Aaron Schobel, yet the Bills have remained with the 4-3.
Nevertheless, DT Marcus Stroud has the size to play nose, while struggling 2006 first round pick DT John McCargo might be a better fit as an end in the 3-4. Moreover, DT Kyle Williams could fit well as an end in the 3-4.
The Bills have two linebackers capable of playing the inside with Paul Posluszny and John DiGiorgio, while Kawika Mitchell seems capable of playing outside linebacker opposite to Aaron Maybin.
Conclusion: I'm not sure if coach Dick Jauron is interested in converting to the 3-4, but I think Buffalo needs to be more explosive defensively in order to temper an offense with a questionable offensive-line.