I think you have to distinguish between guys that Belichick would be investing three years of training, and established vets that can play for you for a couple of years, immediately Before you start out with a three year program why not start with guys that have the size, the speed, the height, and the mental qualities that you want? You can't pay big time draftees big bucks to go to school for several years so developmental players, raw but athletic, would seem the logical candidates and Belichick has obtained a stable full of them.
Derrick Burgess at 6-2 260 4.8, is almost a duplicate of Adalius Thomas. But Thomas is better. The knock on Burgess is that he can't set the edge against the run as an OLB/DE, while AD can and does. Burgess also has been injured the last couple of years, but he does have a couple of double digit sack years, including one year getting 16 sacks. That is as good as Peppers ever had.
Evaluating where Derrick can play, I would say that his lack of run edge setting rules out SOLB, so Pierre Woods,having shown welas an edger sertter last season, continues as the starter there. Vince Redd was positioned at SOLB, and his size makes sense there as a developing reserve. So there is NO CHANGE on the Strong-side OLBs. Perhasp CRabel migh tbe shifted ther for experience and to offer some posible pass rushing on obvious passing downs.
Derrick would join the WOLB pass rushers for playing time. That means AD, TBC, Crabel and Burgess are all fighting it out or platooning at WOLB, the primary pass rushing position. On passing downs, or maybe other times, Burgess may allow AD to swing inside to provide a ILB blitzing capability, like Tedy used to have, in his heyday.
But I think it is likely that AD will have to stay at WOLB almsot full time, because TBC and Burgess are not edge setters and Crabel is still raw and a question mark, as far as edge setting is concerned. But the acquisition of Burgess would still likely free up Thomas to play some ILB, should that be necessary, and improve that crew from Mayo, Guyton, Tedy to Mayo, Guyton, Tedy and Thomas, McKenzie (IR). That foursome would be a very solid ILB contingent, and deeper than the Patriots have ever had there, in any year.
IMHO, Burgess is somewhat redundant, but OTOH, he does add some more experience to the WOLB position, and improves the ILB situation as he might free AD to go there in an emergency.