You can help with the cutting issue by adding some players (works on NBA trade machine)
Boston - Beverly, Williams, Zubac, Kennard, Kabengele, Mann, 3 million cash, a pick swap or two
LA - Walker, Edwards, Green
Boston can then either cut or trade Kabengele, Mann, and Semi
I like that trade a lot better as I do think Zubac and Kennard would have a role long term and Beverly and Williams are solid enough for this year.
So post-trade
Ball Handlers - Beverly, Smart, Teague, Pritchard
Wings - Brown, L. Williams, Kennard, Langford, Nesmith
Swings - Tatum, G. Williams
Bigs - Theis, Thompson, Zubac, R. Williams
Much deeper team, better bench balance, and two quality younger players to help with long term team building in Kennard and Zubac. With Walker's injury concerns the team might even be better this year, but I do like it long term a lot better. Salary is basically the same, so the TPE is still in play and it makes it easier to trade guys like Langford when you have Kennard.
I do have concerns about trading Kemba basically a year after he signed, but in this trade you are sending him to a real and actual contender so I think some of the negative aspects of that are lessoned a great deal.