Spurs need shooting and Malik Beasley could be the answer for them as a prototypical 6th man. This also allows them tho get off of Devin Vassell's contract who clearly has some questions about his potential fit long-term with their growing guard rotation.
Grizzlies get a fantastic energy big who brings the same toughness they lost after losing Dillon Brooks. To me, that is their biggest need in the locker room, a TOUGH guy. Someone who vouches for his players and embodies the grit and grind spirit which is what Isaiah Stewart brings. They also get a nice project player in Bobi Klintman who can stretch the floor and fill in what they're losing in Aldama's place.
Pistons get two elite role players for Cade Cunningham. Two-way players who stretch the floor and offer versatility to their roster going forward. This would likely mean they would have to trade Jaden Ivey for a center, but given the Dallas situation, I would be Daniel Gafford is a guy they could get for a reasonable price.
Potential lineup
Cade, Vassell, Ausar, Aldama, Duren/Gafford