I hate trading healthy players for injured players, but I think I would make an exception for Kawhi, assuming he passes his physical. I would seriously consider moving Griffin to center, at least for half of his minutes. I would also look to trade Johnson, since we would not need him at SF.
Yeah, we can't offer picks like others can but we can offer a really good player in return that a lot of teams can't. Sure Boston has great draft picks but I can't see anything else that would entice the Spurs. Drummond trumps Jaylen Brown, Tatum, or Rozier on a 1 for 1 basis. Celtics need to get bigger. I don't think they have a need for Leonard. I would think Philly has the best shot. They can offer Saric, Fultz, Covington, and picks. That's a heck of a package. I could also see Milwaukee making a run by dangling Parker and Middleton. The Lakers if they don't get Lebron could offer Kuzma or Ingram. Yeah I don't think in any scenario we'd have the best offer but we'd be in the discussion at least.
I don't think the Celtics would be willing to offer more than Drum. They already gave up multiple assets for a SF last summer, and likely will want to see him play healthy next year.
Philly would probably benefit the most from adding veteran leadership to a young and talented team. I would trade Embid for Kawhi to avoid giving a massive contract to an oft injured player, but I don't see the 76ers giving up their potential superstar center.
The Bucks deal sounds like what will happen if the Spurs decide to trade Kawhi. They have a great player already, and could add another without gutting their entire team. Parker is oft injured and thus has not been a key factor in their success. Losing Middleton would really hurt, but Kawhi is even better, and would provide some much needed player leadership.