This might be the most likely combination of players to get the job done. The Spurs would give up one superstar, but receive two players with very high ceilings in return.
Parker would be the X-factor in this deal, as his future is very much up in the air. He’s a restricted free agent so this deal would have to happen after July 1 when free agency begins. The Bucks could sign him to a deal, having pre-arranged a trade and all parties knowing what the plan is. However, depending on how much Parker signs for, other players might have to be added in on the Spurs end in order to make the salaries match.
The Bucks should also be willing to throw in a draft pick or two or a guy like Wilson or Maker. That may seem like an extremely steep price, but the chance at acquiring Leonard is too good to pass up.
One thing Milwaukee may want to look into beforehand is Leonard’s willingness to stay with the team long term. He’s owed just over $20 million in 2018-19 and then has a player option for $21.3 million the following season. The Bucks wouldn’t want to give up all these assets for a one-year rental. There’s certainly lots to think about.