Philly can theoretically clear out space to sign LeBron then move Covington, Fultz, Saric, Miami's 2021 pick and Parsecniks for Kawhi and Mills.
Simmons, Kawhi, LeBron, Illyasova?, Embiid
with Mills, Beli, and whomever to fill out the bench could be the 18-19 76ers roster.
Boston isn't giving up Tatum, I don't see it, but the might give up the stable on all of their previously acquired first rounders in a deal. If Boston gets into a bidding war, then Tatum's available may change but I could see a-
Hayward, Brown, 2019 Kings Pick (probably top five), 2019 Memphis Pick (probably ends up being in the 10-14 range) and the lottery protected 2019 Clippers (same protections in 2020 but unlikely to actually convey) for Kawhi and Gasol.
That is an all-star caliber player, along with a young starter with high upside, and probably a top 5 and 14 pick in next year's draft that is a great haul, the Spurs can stay good for at least a couple of seasons while also being able to integrate two lottery picks into the system, on top of Brown and Murray.