You can get away with rolling a solid top 4, a top 4 which you can find via alternative ways besides wasting Reinhart's value so early by trading him. Reinhart can BECOME a #2 C, which IMO is his ceiling. One of the key aspects of coaching in the playoffs, is matchups. With Reinhart being a #3 or #2 C, depending on how he develops, the Sabres could potentially give teams problems much like Toronto did offensively. We have seen Reinhart play the center position, and play it well. Unfortunately, our former coach couldn't see it and was an example of the microcosm of the issues that Dan had.
As much as people think we're in trouble on the backend, I don't believe we're that far off. Kane is our best trade chip RIGHT NOW, that won't have long term complications of depth down the line. For me, it's easier to stomach any combination of wingers to fix the issue of depth of defense than it is to use a Center for trade bait.
Right now, the league is focusing on getting more offense from the backend with more offensively gifted players on defense. I think we should get ahead of the market turning to finding defensive specialists for teams. Strike now and get your shutdown "defense pairing" and to do so I think you could buy low on a defensive player and allow you the time to develop these type of defensemen. Tanev would be a great example of this, and using Reinhart for this would be overkill. Using a guy like Kane as your center piece would be close, and we have the draft picks(especially early in the rounds) to balance out, if there is any, inequalities.
Pittsburgh right now is playing with a "pedestrian" talented defense, but they have guys playing their roles well and using their forward depth and the center spine(when healthy) to overwhelm teams.
IMO, I think getting a defense looking like: Risto, Kulikov, Tanev, McCabe would be a decent start with Tanev anchoring the 2nd pair and Risto Anchoring the 1st pairing. You then focus on building that defense more through drafting while your team is in playoff contendership with the center spine of Eichel, Reinhart, ROR. With the starting defense, that is a playoff contender defense to start with. On the 3rd pairing you then have Bogo, Guhle(maybe), and/or a free agent signing with Gorges as your 7th dman. This year you draft the BDA, and continue to develop your guys.