I think that Megna has been solid this year. He's only pushed out the line-up to play Beauchemin and Bieska. He's better then Beauchemin and much cheaper then Bieska. Behind Lindholm and Fowler in the depth chart, I think he would be fine on the LS of our 3rd pairing moving forward.
With that said, I think that Larsson is somewhat expendable. He's NHL ready, but is stuck behind a logjam and we really need help at foward. Therefore, I would suggest we move him for a young C in Zacha. Zacha is a former 6th OA pick, but has struggled in NJ and isn't in Hynes and Shero's good books. He's been a healthy scratch a few times this season already. I see the skill in his game, but he's clearly in a role he doesn't belong in. With Hischier looking like a future stud #1C, Zajac acting as a great 2C and with Mcleod in the system, he may be available for a LS D-men.