If the cost for Umenyiora is a 2nd round pick I would trade the Pats 2nd for him in a heartbeat, IF they could sign him to an extension. He's a disruptive force off the edge and would add that missing dimension that could make this defence absolutely dominating. He not only creates pressure and racks up sacks, he is a turnover machine. 10 forced fumbles in a SEASON is incredible. I wouldn't be too worried about his fit in the 3-4 because of the amount of time the Pats spend in sub packages. And BB is great at adjusting the system to fit players strengths so I think he could do some amazing things with Osi. Plus we would still have two 2012 1st's and Oaklands 2012 2nd round draft picks.
In terms of signing him to an extension and fitting him into the cap I think they could make it work. They are re-structuring Haynesworth's and Chad's contracts which is holding up the trades, but the key to the cap is Mankins. Whether they extend him or trade him, I don't see him here playing out the year under the franchise tag because it handcufs them too much. Ideally they could re-sign him and make a few other moves that could create enough cap space.
For example
Re-sign Mankins ($4-6 million cap saving)
Cut Nick Kazcur ($3,095,000 cap saving)
Trade Brandon Meriweather ($1,395,000 cap saving) (possibly Dallas for a 2nd or 3rd)
Cut Marcus Stroud (850k cap saving)
Total- $9.5-11.5 million cap saving
Re-sign Matt Light
Re-sign Jared Page
Trade for and extend Osi Umenyiora
Some other cap savings if these players don't make the final roster
Wilhite (750k)
Levoir (240k)
Slater (150k)
Cohen (150k)
Murrell (150k)
Pryor (75k)
Clayton (75k)
Total $1.5mil savings
(cap numbers based on Miguels Cap page)