Interesting if they use a lot of 3 man fronts, considering there's absolutely no one of value at DT behind Brown, Knighton, and Branch (who's on NFI). However, 4 man fronts present the same depth dilemma with linebackers, since we have nothing behind Hightower and Collins.
Consider a fantasy world in which the Patriots aren't always in a sub package. Which front 7 would you prefer?
Collins - Hightower - (Freeny/McClellin?)
Sheard - Brown - (Knighton/Branch) - Ninkovich
Sheard - Collins - Hightower - Ninkovich
Branch - Brown - Knighton
I'd definitely prefer the second option to keep that bad 3rd LB off the field and put another good DL on.
Of course, in the real world, they'll always be in sub, making the 4-2 the most appealing option with the DTs rotating for freshness.
Regardless of alignment, I think we're in deep trouble if any of our top DT or LB miss extensive time.