Piggybacking off this, I think with the Robertson selection, attaching Rykov or Lindgren + a draft pick to take on Smith is somewhere in the ball park. Theoretically, you could make the deal bigger by attaching a better, more premium asset, but that would involve getting something better back in return. In that case, there would be too many moving parts.
K'Andre Miller will be ready by the end of next season -- I think his development mirrors Kreider/Stepan A LOT because I think he's actually ready right now, but one more year dominating at the collegiate level will do him wonders.
Nils Lundkvist will likely follow after that, possibly at the start of the 2020-21 season, unless the organization decides starting him in Hartford is a better idea. Lundkvist already looks very polished in the SHL, and has the skating ability to transition into the NHL.
Rykov, Lindgren are now just... "there." With Robertson, the organization has made it a priority to select tall (6-foot-4) defensemen (like Miller) who possess the ability to skate with high IQs and win board battles. The Rangers' strength in the pipeline is on defense now. There is depth, and not everybody will reach the NHL.
If Hajek is as good as he was last season, and Miller maintains his level of production, Rykov AND Lindgren are both blocked. With the addition of Fox and development of Lundkvist, the Rangers could explore the possibility of attaching Deangelo with Smith and getting an actual return with shedding the salary as well. There are quite a few options in play now that can make them significantly better this season.