Vegas would do that deal in 2 seconds. They have nothing of note on the right side puck mover wise. Theodore is not a PP QB. His playoff offensive output is a complete fluke much like McDonagh's was. They need a PP QB in the worst way and their lack of offense on the PP is really showing up vs Dallas now. It's much harder to get a PP righty QB than a Tuch. Rangers have no need for Tuch now that they will draft Lafrenierre and added Kakko last year. Holden and Martinez are 33. They have one righty d man and he has virtually no puck moving skills. What Vegas wants means nothing. It's what they need. Nobody is going to take Stastny or Marchessault. Stastny is 34 and makes 6.5 for 2 more years. Marchessault is small, 29 and makes 5 million over the next 5 years. Vegas is stuck with them or has to buy them out. Nobody will be doing Vegas any favors.
Plus if you look at their farm they have Glass who is a big center prospect and Krebs coming in a couple. They have nothing on the farm of note d wise. Especially right handed d. Guy the Rangers should try to get is Glass. I'd gladly give up DeAngelo and Chytil to get him. I don't know if they would bite on that. They might be able to steal him. I think with the hype he got that Vegas expected him to produce more in his debut. So maybe that offer would be enough to get them to give him up. DeAngelo would fit that team like a glove. They built that team to win now with their moves for Stone and Pacioretty.
So much to dissect with your ramblings...
Let's start with your assertion that nobody would want Stasny or Marchessault.... First of all Stasny has one year left on his deal, not 2. He's overpaid, but not unmovable. Hell there was talk on this board of the Rangers kicking the tires on him as a placeholder. You might not think so, but Marchessault would draw interest around the league. He's a 50+ point winger on a reasonable contract, who plays physical for his size. Might not be a huge return, but again he's not untrade-able.
You're correct the Knights are extremely weak at RD & they don't have a offensive capable defensman in their system. DeAngelo would be absolutely be a great add for the them, but that doesn't mean they'd be willing to part with Tuch to get him. Even if the Rangers weren't stacked on the wing, I assure you Tuch wouldn't be heading to NY.
The Knights would probably trade one of Glass or Krebs for ADA & Chytil, but salary would have to come back to the Rangers since the Knights are basically capped out & trying to retain Lehner. I don't think the Rangers would make that deal, however.
Finally, since you brought it up...Theodore's playoff output is no fluke. The guy is a rising star who is having a breakout season. He may not be ADA on the PP, but he's twice the player ADA is defensively. VGKs problems on the PP is a scheme issue, not a Theodore issue.