At both ILBs, SILB and WILB, and the flexibility to swing to OLB, flexibility that BB always seeks. He is a probable 3 down ILB, as he is good against the pass with his 4.55 - 4.6 speed, just like Mayo. Most ILBs are too slow if big; or to small if fast, for the two gap 3-4. He fits on both criteria.
That would cement the LB corps for a decade. His speed would help shut down the short pass over the middle. He is a very smart, film room rat, and strives to get better. BB wants intelligent players who comprehend the Defense and could call/set the D, if needed. The position that BB prefers to do this, is the ILB since their voice would carry over the whole D. Sure Mayo appear to be able to do so, but what if he goes down?
I agree that there may be better pure 2 down SILBs, like Maualuga. Who wants 'em, I don't as high draft picks. They are situation substitutes for 2nd day selection. Teams have gotten smart, they pass on 2nd down when the 2-down, poor pass defenders are in.
The Pats would probably like a great SS to help the pass but the cupboard is bare, in this draft other than maybe Moore, since the one sure blue chipper, Mays is not coming out.