A suggestion for the early going.
Marchand - Bergeron - Czarnik
We know you can pretty much put a broom-stick with these two and they'll have some success. Give them a skilled little puck-hound who displays a willingness to play a two-way game.
Spooner - Backes - Pastrnak
Maybe with Backes as the safety valve up the middle, Claude would be more willing to re-unite Spooner and Pastrnak. We know they have chemistry, and even though it's only one game, Backes and Pastrnak seem to have chemistry as well. I like Spooner instead of Heinen because he can skate with Pastrnak, whereas Heinen isn't really a burner, more a smart cerebral type.
Heinen - Krejci - Hayes
Krejci likes to handle the puck and make plays. He seems to be at his best with slower guys who let him play his cerebral game. People may hate Hayes on Krejci line, but he's a Bruin, doesn't fit the 4th line, and I don't know what else to do with him. If he can't produce alongside Krejci, when Vatrano is ready to go, Hayes goes to the press box.
Belesky - Moore - Nash
While I don't like a 3.9 million guy on the 4th line, Belesky has the type of skillset that can play any line, even the 4th. You could give this line a solid 11-12 minutes a game and they won't hurt you. In game situations if a young guy like Heinen or Czarnik is struggling, you can quickly adjust and move Belesky up. As we move forward here, given the depth in left-shot young prospects, we can't just hand over a prime position to Belesky based on what he's paid. Back in early 2008-09 when the Bruins were running through opponents, Kobasew found himself on the 4th line at times. That's depth folks, it's a nice problem to have.