There's some good stuff here overall, but to pick and choose:
1. Celebrini - awesome, but I'm not banking on anything. I'm assuming the pick is 5OA (seems like a safe bet we pass one of Arizona, Ottawa, or Montreal; or get leapfrogged by a team farther back winning one of the lotteries), where I'd like to see one of Levshunov (to get another blue-chip RD in the system), Lindstrom (size and skill with a high floor?), or Catton (skilled play-driving gamebreaker we're lacking), whoever is still available at 5OA if Celebrini and Demidov are also top-5.
2. Vogelhuber and Nash I'd be very happy with, but...
Quoting: squashmaple
Nash and Vogelhuber are both probably the future, but not yet. Bring in veterans for both jobs now with eyes on promotions, a la Sakic to President and MacFarland to GM in Colorado
...I don't hate this idea at all either. Of the two, I'd rather have Vogelhuber now and let Nash get some more seasoning.
3. Laine - I'm 100% on the "keep Laine" train. Trading him is lose-lose-lose: getting a bad return on his lowest value, while also losing a potential 40-goal-scorer PP specialist we also need, while also being a bad look on the team, trading a player hopefully (and likely recently) out of the PAP. At worst, he comes back next season and flops, in which case we've lost nothing. Might as well see if he can regain form, and then either trade him at TDL or keep him.
4. I like the idea of trading for a center, but I think it's better served to take the leap of faith that Fantilli can and will be a 1C and go for someone who can be a good 2C. Jenner and Voronkov I like on the wings, and SIllinger looks like he's ready to be that defensively-responsible two-way 3C right now. Trading Johnson to do so, though, is also unlikely and not a great look considering his injury.
5. Elvis - I like that, but NJ may not go for it. Even if we send up to a late-round pick for Allen (a 5th + Elvis for Allen alone), I'd be very happy with that. Again, you've got to take the leap that either Tarasov or Greaves will take the reigns, but likely not next season. Having that seasoned 1B guy would be perfect for one more year of transition, and if it's not Allen, it could be a UFA like Stolarz, Rittich, Talbot, or Jones.
6. Mateychuk - I wish he was AHL-eligible next season...definitely nothing left to prove in the WHL, but he's not a 3rd-pair guy stylistically, and he's blocked by Provorov as long as he's here. I think you have to have him on the NHL roster next season and look to move Provorov closer to January than TDL if Mateychuk looks promising. We could probably use an insurance veteran 7th D on a cheap deal for a couple of seasons for that scenario, and for NHL depth/3rd-pair minutes.