This is essentially what I'd do. You can obviously tweak these trades or do similar ones
Trade 1 with Houston
Brown for Sheppard, Brooks, Smith, Eason, 2025 1st (10), 2027 PHX 1st, 2028 HOU 1st (you may not be able to get both of those future picks, but you try)
Trade 2 with Detroit
Porzingis for Stewart, Fontecchio, 2026 DET 1st (lotto protected)
Trade 3 with San Antonio
Holiday for Vassell
Trade 4 with Brooklyn
Hauser for 36 and future protected 2nd
Trade 5 with GS
White for Hield, Podz, GS 28 1st
New roster for next year
PG - Sheppard, Pritchard
SG - Vassell, Podz, Fontecchio
SF - Brooks, Hield, Scheireman
PF - Smith, Eason
C - Stewart, Tillman
10 + 28 + Tatum on IR + 36 (Stash or 2way)
Cut or dump Walsh
That team is not the worst team in the league, but a clear lottery team. I don't think you'd need to do the White trade either, but the idea of getting a way in the future pick of GS was appealing and I do like Podz.
Summer of 26 the guys under contract for 26-27 would be Sheppard, Vassell, Pritchard, Podz, Brooks, Hield, Stewart, Tatum, Scheireman, 10, 28, BOS 26 Lotto pick, Det 26 non-lotto pick. I'd move some of the guys from that list at the deadline next year for an expiring contract to free up a max or near max slot, but even if you didn't you can use them as the salary filler in a trade for a star.
You then use the cap space for a complimentary piece to Tatum while still having lottery picks and future picks to use in a trade along with guys that can be salary filler.
That is the type of overhaul the team needs to win a title any time in the next 5 years. Minor moves or moves that don't yield high level draft picks isn't going to get the team there.