If I knew, I would be on staff. The idea about this defense and vets versus young players came to the forefront last year in a couple of articles.
I believe that Capers is more static than his reputation, though he does gamble on blitzing. So dreaming up a new D scheme isn't going to happen.
I think a lot of this goes back to Belichick's comments about switching back to a 4-3 from the hybrid. There is less teaching time, just as many injuries (maybe more with concussion protocol) and the salary cap takes vets away. So they can do less advanced tweaks and are looking to limit the amount of installations. So they run a 4-3 as base rather than a 3-4.
I think the confusion this offseason about less volume more player groups points in a similar direction. Less tweaks, more alignments with specific personnel. Its a giveaway to some degree by watching substitution patterns. So they need to put better players on field in best position to maximize chance to win individual battles.
wist has a point about the 3-3 nickel. It would help from an installation standpoint (less for young D lineman to learn). I just don't think they can run it without pulling Matthews out of the pass rush.