Wouldn't do this with Bradley. He's too young and has too much upside to throw away for a late first round pick. Even if he never develops beyond the player he is now (17 points, 5 rebounds per 36 minutes, 45% FG, 40% 3PT, former All-Defensive first team) you're still unlikely to replace that with a 20th overall pick.
The only reason Boston got Sullinger at 20 was because teams were scared off by his bad back, and even still Sullinger is nowhere near the elite future superstar that people on CB seem to think he is. He's an inconsistent, undersized PF who lacks athleticism who might one day be a very good player...but still has a long way to go. It's debatable as to whether he is any more valuable to Boston than Bradley is right now.
I'd only trade Bradley for a pick if it's top 6 or so, and no team is offering that.
I also wouldn't do it for the expiring contract - Bradley is expiring himself, and Bogans is non-guaranteed so he's basically an expring too. This makes no sense other than to get rid of Bass, and Bass' deal contract ($7M/2) isn't THAT ugly that you'd take such a one sided deal just to get rid of him.
If the deal contained Jeff Green and somebody else in return for Okafor and a late first rounder, then I'd do it. Green's deal is big enough ($9M) that it's worth clearing, and at his age he doesn't have much upside...you'd take the gamble for a ~20th pick and a nice expiring contract. For Bradley though? No. I think we could get a better return for him if we were more patient.