I think the "heart" discussion is a little overrated in Boston. Team needs a) better players, and b) indeed ones that compliment each other.
Leaving aside the obvious near-term small stuff -- Schroeder over Smart, Nesmith taking some of Richardson's minutes -- the Cs are finally going to have to face this question (likely without choice) between now and the FA period next summer:
What is the best possible package they can get for Brown, Smart, and filler (Richardson, Horford) and / or picks in one or two large trades?
Because if Stevens doesn't get serious on that topic, there's significant risk teams will smell blood in the water (namely: Tatum being unhappy), and the value of the package will go down as the Cs hand is forced due to spiraling locker room and floor fit issues.
My personal feeling is this: if the Cs traded every player on the roster today other than Tatum and Bob Williams, i'd be 100% ok with that. Because in the next couple seasons, I bet that's exactly what happens.