Kawhi is still an elite asset in the league, so it would take Hayward, Tatum/Brown, a top 5 pick and more. The Spurs might actually value Marcus Smart because they can turn him into a consistent 45% 3pt shooter, and that would make Smart one of the best role players in the league. Hayward, Brown, Smart and a top pick might get it done, IMO, which would leave Tatum as a chip to use for Davis. Maybe something like Horford, Tatum and several 1st round picks for Davis.
Leaves Boston with:
Kyrie Irving
JJ Redick
Kawhi Leonard
Anthony Davis
Marshall Plumlee
and no 1st round picks for a while.