I'm gonna go with suggestions, because predictions are near-impossible (who saw us signing Kemba and Kanter coming?)
Trade no.1:
https://tradenba.com/trades/I2HX7zg0H Boston receives: Nikola Vucevic
Orlando receives: Gordon Hayward, Romeo Langford, pick #26
Why for Orlando: receive a huge expiring contract and get rid of Vucevic's big contract, which doesn't fit with the age profile of Isaac, Gordon, Bamba and Fultz. Get a guy just picked in the lottery and another first round pick.
Why for Boston: get an elite offensive big-man who can pass, rebound, shoot and score, and he's not a terrible defender (underrated in my opinion because he's unathletic). Tough to move Hayward given his rotten luck but at least he gets to be taxed less, right?

Trade no.2:
https://tradenba.com/trades/ukhXbIVE6 Dallas receives: Kemba Walker
Boston receives: Tim Hardaway Jr., Seth Curry & Justin Jackson
Why for Dallas: based on the presumption that a) Hardaway takes his PO and b) they believe Giannis when he says he won't leave Milwaukee, I think Dallas would realise that they need a 3rd wheel. Got exposed in the playoffs without KP and with Doncic hobbled. Still leaves them with DFS, Brunson, Dwight Powell and Boban as role players.
Why for Boston: adds some much much needed shooting in Hardaway and Curry, who are both comfortable starting and coming off the bench. Sheds significant money without Kemba, and Jackson is immediately a better Ojeleye.
Draft Kira Lewis Jr. or Tyrell Terry at 14, and Xavier Tillman at 30.
Try and sign a guy like Korkmaz, Glenn Robinson III or Alec Burks in free agency
I'm not even sure these trades and signings are realistic, fair nor smart. But I think a team of the following is quite solid. Really just an excuse to vent about what I want more than anything
Smart / Lewis Jr / Waters
Brown / Curry / Edwards
Hardaway / Burks / Jackson
Tatum / G Williams / Tillman
Vucevic / Theis / R Williams