I'd be intrigued by Barnes + Whiteside. That's two players in their prime who play both ends of the court. Best shot blocker in the league added to a strong on-the-ball defense. Having an elite shot blocker behind Smart, Bradley and Crowder would allow them to apply even more pressure. What a nightmare for opposing scorers, to be pressed by Smart or Bradley, switched off to Crowder or Barnes, and if you beat your man you have to score over Whiteside?
Our rotation a year+ out could be something like this, with all of those 2nd tier guys getting some starts especially early on. Barnes has also been a very effective stretch 4, so starting another guard and moving him there could be an interesting wrinkle.
Smart / Barnes / Ingram (BKN pick #3?) / Sully / Whiteside
Thomas / Bradley / Crowder / KO
Rozier / Young / Hunter
Barnes + Ingram + Sully + Whiteside would be a lot of scoring punch (all 15-20 ppg ability) while Smart and Whiteside are both All-Defense level at the 1 and 5 spots, and Barnes + Ingram give a ton of length, and Sully focuses on team defense with Whiteside guarding the rim.
We'd still have all of our chips, too. Obviously that core looks amazing with a Durant etc coming to town, but that's a given.