Myself I would look at the depth chart like this
Connor-Scheif-Vilardi (hot and cold)
Nino-Lowry-Ehlers...Appleton to me is the only player that doesnt make that a true 2nd line. And I'll add that Lowry going forward into his next contract will likely look to be a more prominent player, no matter where he plays, because he's battling with the best and winning a lot of battles night in night out. And a lot teams need that kind of player. And we have him as our captain.
Perfetti-Namestnikov-Chibrikov (IMO Cole looks best when he plays with another finisher, and Chibrikov is all finish, Ehlers and Lambert are more dash)
Iafallo-Kupari-Appleton, the kind of line you trust in a defensive zone draw to get the puck out of the zone, Kupari is maybe the weakest on the boards of the 3, and that's where I see room for improvement. Maybe that improvement is Namestnikov and Chibrikov and it balances out.
If Ehlers isn't pigeon holed he has the potential to move up on that top line when it needs a spark, and maybe Vilardi moves around, and Chibrikov too.
Barron-Gustafsson-Lambert would be my replacement level line. Cozens beat Lambert in a neutral zone race so I think he can move pretty well. Lambert won't get a lot of rope at C in a veteran league on a playoff hungry team, but I could see him being effective in the same spot Appleton is in now. Game is easier to play when you have workhorses on the boards.
I do think C is the number one position of depth needs for the Jets until the Yager bomb arrives. But if the Jets want to reward Lowry for all the hard work, I'm not sure another $7 million center makes it easy to manage the roster going forward. Although replacing Ehlers with younger wingers seems more possible than it did last year.
Mc Leod is an excellent penalty killer, he showed that in the playoffs last year, I like that option a bit more at a better price.