It's a fair question, but you need to define "enough"? If Sweeney gets two B guys, will people think he did "enough" to defend his job? Probably. Like Nash last season...he did something and it wasn't totally trivial. It wasn't going to be enough to allow them to cmpete for a Cup and everyone knew it, but it filled a hole and made them more capable. If that's his goal again, then 2 B players does the trick. They'll be knocked out by Game 6 in the 2nd round, at very best, but it would "help". If instead you define "enough" by standards that maybe Bergeron or Chara themselves would hold him, meaning giving them a REAL chance to compete for a Cup, then only an A guy or equivalent plus a B or C does the trick, IMO.
For my standards, I've never been about "renting" in the name of one season, and with the holes he's left/created on this team, I think doing so would be foolish. On the other hand, I have been about making a hockey trade to add a bona fide top 6 forward whom you plan to keep, either because they have term, or you will drop a bag of cash on them. That continues to be what I want to see. So a lot of the names in that B list have "Hey look, I made a trade so get off my back!" written all over them. Simmonds, Carter, etc. Those are Nash redux guys, maybe worse. That would be classic Bruins and right in lockstep with Sweeney's past, and thus it's exactly what I expect.