I am not saying arm length is a determining factor, but it is clearly a very important factor in playing as a TWO-GAP 3-4 OLB. Elvis Dumevil, James Harrison, Lamarr Woodley, et al. play in one-gap, zone blitz oriented schemes where the ability of the OLB to set the edge is much less emphasized. Bruschi, who played in this defense for nearly his entire career, has explained this concept numerous times. But fine, just ignore Teddy Bruschi, what does he know? Two-gap, 3-4 OLBs need to be taller, longer players who can prevent OTs from turning them inside. Even the tight-lipped Belichick has explained this numerous of times. Remember his post draft press conference in 2009?
Acquiring talent is not finding just finding the guy who looks best on a highlight reel. It is about finding players who are best able to do things asked of him in your system. SCHEME SPECIFIC scouting. It is something the Patriots have been lauded for numerous of times over the years. To me, Cunngingham is a player who can both be a productive pass rusher and set the edge in our defense. Notice how Hughes and Graham were taken by one-gap 4-3 teams? Maybe you should find a way to fill your contrarian urges by advocating for the Patriots to change their scheme to fit in players like Hughes and Graham. Trying to fit square pegs into a round hole is not "thinking outside the box", its stupidity.
If you want a good resource on how Patriots OLB prototype and the justifications for it, I suggest you check out the following articles:
Positional Breakdown: Outside Linebackers How The Pats Draft
Analyzing the 6’4 4.6 3-4 OLB Prototype How The Pats Draft