If Stepan is dealt, it needs to be in a deal that makes the team better.
And honestly, I don't see how Arizona has any leverage in this deal at all. They can't get free agents to sign there, and acquiring a 1C with term isn't going to be cheap.
Brooks said as much in a recent article: the Rangers have no incentive to deal Stepan for anything other than good value. Trash pieces from Arizona won't get it done, especially when they have good, young pieces that they could easily part with without hurting their rebuild.
As fans, it's easy to overvalue your own player while undervaluing what you want to acquire, but it's all used car salesman type BS. None of the pieces that we've talked about coming back from Arizona are sure things, and the Rangers need to get multiple high-quality pieces to offset the risk they take in getting futures.
Stepan instantly becomes Arizona's best C, and he can take tough matchups (just like he's done his entire career) so that their young guns done have to get thrown in the deep end. Worst case scenario is that Stepan stays here, which I'm more than okay with.