Assuming Zibanejad comes close to hitting his ceiling, Zib-Stepan 1-2 down the middle is good enough to win. The problem with the team isn't the forwards. Trading Stepan opens up an enormous hole, and although theoretically he could bring a top-pairing RHD back, now who plays in the top six? Hayes?
And from there, the Rangers lose their 1C. Who plays the big minutes against the top opponents at even strength and on the PK? Now the Rangers don't have a 1C, and they need an elite one to contend, so what assets are available to trade in a creative hockey trade to get that 1C? Your answer: Kreider, Zucc, extended Zib, the RHD we theoretically traded Stepan for, McDonagh, Skjei and Miller. Miller and secondary assets won't get back an elite C. You create one problem by fixing another, it's a giant step sideways.
The Rangers need to play to their strengths. Stepan isn't elite, but Stepan-Zibanejad-Hayes-Lindberg down the middle 1-4 is one of the NHL's best foursomes. Assuming Lindberg isn't poached by Vegas, it exists for one more season. Miller can also play C in a pinch. What they should be doing more is not thinking about moving Stepan, as much as fixing the cap situation through other means. This means attaching assets (first-round pick and prospects) with Staal to move his contract. That means looking at Phil Kessel/Maple Leafs situation with Rick Nash. Our wing depth is really good. Kreider, Zucc are good top-six players. Vesey will hopefully take a step forward, as will Buchnevich with minutes. Maybe Miller takes another.
For anybody who watched the games, it was evident the forwards are good enough to win. It came down to our defensemen being deployed incorrectly. For a group to be consistently in the top five in GF each season, to have the bad Corsi/Shot Differential #s they did, it means this was strictly a coach/D issue. With Girardi gone, give that money to Smith. From there, figure out the best course to open up the cap space needed to sign Shattenkirk. I think the rest of our depth is still a huge strength. Moving Stepan doesn't fix anything, even if you like to believe opening up his cap space is important. Zibanejad and Hayes is not good enough to win a Stanley Cup, and now you have no open resources available to go out and get a 1C. Organizations should always play to their strengths.