I don't agree that he should already be in the NHL. This past year was the one where he showed that he probably is ready for next year. Probably. If the Jets don't have an appropriate opening then some other team should get him.
I wouldn't do Trouba for RNH. A package of assets we could more easily spare would be another story but I don't know if we could come up with the value to get him then. That would still leave us with the problem of paying him under the cap.
I'd like to see Lemieux on the 4th line before I decide he is the best 3LW we have.
The problem with Lemieux is that none of his coaches in the past have set boundaries for him. He's been allowed to run around on the ice playing like an out of control bully. You can get away with that in Junior and intimidate many of your smaller peers, but that style usually doesn't translate well (or help the team anymore) the closer you get to the NHL. (For some strange reason Wilson has been able to get away with a chippier version this style in the NHL without getting Raffi Torres type suspensions yet.)
Vincent may have spoken to him this year, but I think the changes we're seeing are more because Lemieux, his dad or his agent realized the Jets weren't going to gift him a spot in the NHL with his previous level of play.
I think he had the physical tools to play for the Jets last year, but acted like an entitled millennial and wasn't disciplined enough for Maurice to trust him.
From what I've seen, I'll go out on a limb and say he makes the Jets next year and if he doesn't demands a trade to one of the 30 other teams that will gladly play him. I'm pretty sure that whatever organization he's with he'll be playing in the NHL for 2018-19.
Lemieux isn't just some fourth line grinder and I don't think it's reasonable to automatically put him on the fourth line just because he is starting out. Smart coaches put players where their skillsets belong and where they'll learn the fastest - even if they're just starting out. (Why putting Connor or Roslovic on the fourth line as rookies would make no sense.)
Lemieux is a punishing checker, can dig the puck out on the forecheck, hustles, backchecks well and probably has better hands than anyone currently on the Jets fourth line. Putting him with a skilled center (Little) and a speedy, shifty right winger with better finishing ability (Roslovic) complements his skillset better than anchoring him to a couple of fourth line stone hands grinders like Lowry, Copp or Armia. (Part of the problem that Petan had to deal with when he was given a brief look with the Jets.)
I've posted before what I think the Jets lineup should look like in 2018-19 if the Jets can trade either Myers or Trouba to Edmonton for RNH or Draisaitl (either team adds where appropriate). You usually have to give quality to get quality. Obviously it would be preferable to trade Myers++, but after seeing the Taylor "MVP" Hall debacle blow up in his face this year I'm not sure if even Chiarelli would be dumb enough to trade RNH for Myers++.
2018-19 Jets lineup:
1) Connor-Scheifele-Wheeler
2) Laine-Draisaitl/Nugent-Hopkins-Ehlers
3) Lemieux-Little-Roslovic
4) Copp-Lowry-Tanev
(Armia, Appleton, Vesalainen)
1) Morrissey-Byfuglien
2) Kulikov-Myers/Trouba
3) Niku-Morrow
(Chiarot, Poolman, Melchiori)
1) Hellebuyck
2) Trade for Calvin Pickard
(Comrie - though right now I wouldn't trust him and wonder if he'll be able to turn it around next year like Hellebuyck did this year (until the playoffs). Weak goals on Comrie cost the Moose so many games that I actually felt bad for Vincent and the Moose players some nights.)