Overly complicated. This simple trade should make all parties happy:
Boston Trades: SAC19, Another first round pick
Boston Gets: #4 pick
Boston moves up comparable asset by 1 year at the price of an additional first rounder.
Memphis Trades: Parsons, #4 pick
Memphis Gets: Wesley Matthews, JJ Barea, SAC19
Memphis moves down a comparable asset by 1 year for the reward of getting rid of 1 year of bad contracts. Matthews and Barea are expiring contracts.
Dallas Trade: Matthews and Barea
Dallas Get: Parsons & 1st rounder
Mavs take on 1 extra year of bad contract for a first rounder.