Lavoie's a tough one to forecast, as he doesn't really have a clear spot. But that's not necessarily a bad thing.
Injuries happen, and rather than suddenly being forced to rush Savoie or Jarventie back from injury, having Lavoie on deck means someone going down won't create a cascade effect down the lineup.
As for the 4th line, youth would be nice, but honestly I like the idea of Janmark-Philp-Perry. Good size, some bite, plus defensive accruement. I could also see Lavoie and Perry being a decent 4th line combo if you can get some speed at centre.