I will just do smart for now, but need some more time to think about the others. I think Sullinger would be the second most fun guy to do because, in my opinion, he still has upside if he can lose the weight. However, I will admit he is running out of time to do this.
Marcus Smart
Best Case Scenario - Kyle Lowry
Worst Case Scenario - Lindsey Hunter
Kyle lowry is probably about the same as Smart on Defense right now, perhaps even a slightly worse defender. However, he is miles ahead of smart offensively and can be a really ferocious finisher in the lane. People may be a little low on Lowry at the moment, but I will remind people he was playing hurt for a lot of the second half of the season and in the playoffs so looked worse than he normally is. When Lowry is healthy he is a reserve all-star calibar player.
I will be honest the Hunter one maybe be bad, and I am doing it on more reputation than based on film of Hunter. However, Hunter carved out a really long career for himself as a defensive minded back up. He picked as a double digit scorer for about 5 seasons. I think Smart is already better than banks.