Unless I'm mistaken, the Celtics will only have that cap space if they renounce not only the rights to Bass and Jerebko, but also the MLE, and the two large TPEs ($12.9 mil, $7.7 mil) from the Rondo and Prince trades.
I'd much rather Ainge use those other assets, rather than chase cap space this offseason.
Returning to the Bradley to Utah scenario, I'd much rather send Bradley, Sullinger, and picks to Utah for Derrick Favors. A long shot, perhaps, but Sullinger as a stretch four next to Gobert, plus Bradley, plus picks, seems like a decent haul for Utah if they decide that Favors isn't untouchable.