How about Schroder (5.9, expiring), Pritchard (2.1, 3 years left), and Grant (2.6, 2 years left)
for
Brunson (1.8, expiring) and Powell (11, 2 years left) OR Kleber (8.8, 2 years left)
If Mavs don't want to pay Brunson, they get some cheap, young shooting around Luka in Pritchard and Grant while getting a starting-caliber point guard for the rest of this year to replace Brunson's production.
Celts would have to pay Brunson this offseason, but they get a starting guard that can shoot. Kleber/Powell replaces Grant's role as 3rd big off the bench.