In contrast to the prevailing narrative, I don't think the C's need a superstar to take the next step as a team. Obviously, it would help. But the core problem with this team is a lack of shooting, not a lack of shot creation. All year the C's got tons of open looks, they just didn't make them.
1. We need a stretch 4 who can start. That could be Olynyk if he steps up his game, but it's more likely to be someone else. It's clearly not Sully - Hawks showed a willingness to just abandon him in the mid-range, and he isn't a good enough shooter to make that shot a valuable one. Not to say that we shouldn't keep Sully, but if we do, then we need to replace Amir in the starting lineup (he only plays 20mpg anyway). I don't think there's anyone we could draft that would fill this role right away, but there are multiple good FA options: Ryan Anderson, Chandler Parsons, Nicolas Batum, Harrison Barnes. Of the four I like Parsons best.
2. We need a wing shooter off the bench. It doesn't seem tenable to play Smart and Turner together, even if the other 3 players are all shooters. Turner has played well enough that somebody is going to overpay him. Let him walk, and draft a guy who's going to space the floor. Ingram with the Bkn pick, obviously, and my latest binkie with the Mavs pick is Furkan Korkmaz.
My ideal non-superstar scenario is that we land Simmons + Korkmaz and sign Parsons to the small max (~$22m/yr). Parsons can start at PF (he's 6'10 and he's been effective in that role during his career). Korkmaz + Olynyk will come off the bench with Simmons + Smart to mitigate their lack of spacing, and Smart's ability to guard 1-3 lets you play any of IT, AB, Crowder, or Parsons with the bench unit.