I suspect that most teams will try to deploy a man concept against NE, including the Steelers who have already said as much publicly. It is something with which NE has struggled over the years - post Randy, I suppose - because of their diminutive and athletically limited (comparably speaking) receivers. A healthy Gronk and, as you've pointed out, the addition of the speedy Cooks will make that very very difficult for defenses to execute in reality though. As
@robertweathers stated, this offense is the most diverse we've ever seen (on paper anyway) in NE. It's seemingly built perfectly to play against man and zone coverage. And if Gillislee can provide that extra element to the ground, one with more home run capability than Blount (I really like LG), then I just don't see how teams will stop it.
I normally try not to engage in 19-0 stuff (hate it) and talk of being unstoppable, but at least the unstoppable part has to be on the table here for the reasons mentioned already. If the O can strike a good run/pass balance, it will be a hard day for every team on the schedule. I said it in 2014, 2015 and 2016, and 2017 is no exception - provided health to the key guys and solid OL performance, I don't see any other team in the NFL stopping NE. In fact, I think it applies this year more than ever.